Chapter 2: A Logical Elucidation of Locked Room Tricks

That night, everyone gathered in the dining hall with cheer on their faces. It seemed we'd all breathed a collective sigh of relief now that the locked room had been solved. However, the culprit hadn't been caught yet, so the case was still unsolved. Everyone put that fact out of their minds and enjoyed a moment of peace.

In that relaxed atmosphere, only Sagurioka wasn't relaxed. He stole the occasional resentful look at Mitsumura. He seemed extremely upset that someone had managed to solve the locked room mystery before him.

Meanwhile, I noticed something else. After we finished eating, I asked Miss Meirozaka about it.

“By the way, what happened to Mr. Yashiro?”

The dining hall was full of guests, but there was one person missing: The trading company president, Mr. Yashiro. Miss Meirozaka responded to my question with an “Ah.”

“Mr. Yashiro might have gone home.”

I couldn't help but respond “Eh?” and raise my eyebrows.

“Even if he went back, the bridge is still down, right?”

“Yeah, it is,” she nodded. “So he headed into the forest. That was around noon, way before Miss Mitsumura began her deduction show. Shihai and I tried to stop him, but he shook us off and ran for it. We tried chasing after him, but we couldn't find him. It would have been dangerous to go any deeper into the forest, so we had no choice but to turn back.”

“...”

In other words, Yashiro was almost certainly...

“He's probably lost,” Miss Meirozaka said calmly. “This isn't the sort of mountain an amateur can climb down without a map. But even if we wanted to call the police on him, we can't.”

“Because the phone lines have been cut.”

I was astonished. I hadn't expected we'd lose someone like this.

I took a deep breath.

“Why did Mr. Yashiro go so far just to escape this hotel?”

“Well, even if you ask me, you should have an idea of your own, right?”

“Do you have any?”

“He thought he was going to be killed.”

The declaration was a bit creepy. She was saying Mr. Yashiro believed that there would be more murders in the future.

“By the way,” I said, mostly just trying to change the subject, “Would you show me the security camera footage later? I saw there was one at the gate.”

The House of Snow was surrounded on all sides by a 20 meter high wall, so the only way in or out was through the gate. And that gate had a security camera.

Miss Meirozaka tilted her head.

“I don't mind, but why?”

“To eliminate the possibility of an outside culprit.”

Since the bridge had been destroyed, the hotel had become a closed circle. But that didn't mean the culprit had to be one of us. There was also the possibility that someone hiding in the area had killed Kanzaki. However, if we checked the camera at the gate, we could eliminate the possibility of an outside culprit. There was no way to kill Kanzaki inside the building without passing that gate. In other words, if there was a third party culprit, they'd definitely be seen on that camera. Therefore, if the third party wasn't visible on the camera, that meant the culprit was definitely among us.

When I explained that, Miss Meirozaka made a lousy response.

“But what if the culprit had been hiding inside the wall for a long time already?”

Her argument went like this: According to her, the security camera footage was overwritten and deleted after a week. Therefore, if the third party had snuck through the gate over a week ago, the footage of them no longer existed. The culprit then hid inside the walls of the property for about a week before killing Kanzaki.

It was a pretty absurd theory, but the most upsetting part was that I couldn't completely deny it. When I gave her a sour look, Miss Meirozaka said “Don't worry.”

“I check that camera footage every day, and I have since this hotel opened over two years ago. Even when I leave for my days off, I check all the footage I missed when I get back. That's why if a suspicious person were to enter through the gate, I'd definitely notice it.”

I see, I think. Hesitantly, I asked.

“So, was there a suspicious third party?”

“Lucky us, no there wasn't,” she told me. “I also checked the footage from yesterday already.”

“I see, so we can completely rule out the possibility of a third party culprit. No, wait, there is still the possibility that the culprit snuck in before the hotel even opened.”

“That's ridiculous.”

“But it is possible, isn't it?”

Miss Meirozaka shook her head.

“No, it isn't. If you wanted to stay hidden for over two years, you'd need two years worth of food, right? If the food storage decreased by the amount necessary to keep an adult alive every day for two years, we'd definitely have noticed.”

“But the culprit could have brought two years worth of non-perishable food from outside.”

“That would be quite a lot, wouldn't it?” Miss Meirozaka replied immediately. “There's nowhere in the garden you can hide that much stuff, so the culprit would have had to hide it somewhere inside. But, every year Shihai and I clean out the whole place. We clean the entire mansion every spring, so if the culprit had two years of food with them, we would have found it during one of those.”

“Hmm, I see.”

I groaned. So in other words, we could definitely rule out the possibility that a third party was the culprit. Which is to say, the culprit was someone we knew.

As I was talking to her, it came to me.

“Miss Meirozaka, did you see anyone on the security camera last night?”

“What do you mean?”

“The bridge was burned last night, right? To set the bridge on fire, you'd have to go outside the walls – which means, the culprit should be seen on the security camera.”

Miss Meirozaka thought for a moment, tracing her memories back, then finally, she shook her head.

“No, there was no one in the video.”

“Hmm... Then that means...”

Did that mean the culprit had planted a timed ignition device or something on the bridge before arriving at the hotel? That meant this was a premeditated crime. If the murder was committed impulsively, it would be impossible to plant an incendiary device in advance.”

“Did they plant some sort of mechanical ignition device with a timer?” Miss Meirozaka asked.

I replied “They might have, but there's an easier way. For example, they may have made an incendiary device using yellow phosphorus. Yellow phosphorus has the property of igniting when it comes in contact with air, so it's usually stored in water, and you can use that to create a timed ignition device. For example, if you wrap yellow phosphorus in absorbent cotton soaked in water, over time, the water in the cotton will evaporate and the yellow phosphorus will eventually be exposed to the outside air.”

“I see. It seems like anyone can make that without any special skills or knowledge.”

Saying that and nodding, Miss Meirozaka said “So you mean anyone could have burned the bridge?” She put a hand on her chin and gave me a thoughtful look.

I woke up at 5:00 A.M. the next day, and even though I remained under the blankets for five more minutes, I couldn't get back to sleep. Reluctantly, I changed my clothes and went to the lobby. Most likely no one else was awake yet, but I thought it would be better to kill time there than by sitting around in my room.

But when I arrived, there were already people there. Riria and her manager, Mr. Manei, were there, and surprisingly, so was Yozuki. And I thought she hated mornings.

“Hey, hey, Kasumi, this is amazing!” Yozuki excitedly beckoned me over. Then she turned to Mr. Manei. “Manei used to be a fortune teller.”

I didn't follow. I looked down at the table and saw an array of tarot cards laid out. Things were starting to make sense. Mr. Manei had used these cards to read Yozuki's fortune. And she was amazed at his skill.

“Servant boy, you sit down too,” Riria said. “Manei is going to predict your non-existent future.”

I sat down as instructed, sighing all the way. “Is there anything in particular you'd like to know?” he asked. I thought about it a bit and asked the first thing that came to mind.

“What I want to know is who's the murderer.”

Riria kicked me in the shin. “Don't be rude, servant boy,” she said in an icy voice. “Just ask if you'll be lucky in love or something.”

“Yes, ma'am.”

“Alright then, luck in love,” Mr. Manei said with an impatient look at the troublemaking Riria. Ever since yesterday, Riria appeared to have completely taken off her cutesy mask, but even under those circumstances, seeing her physically abuse me, a normal person, must have been stressful for a manager.

The sound of cards being cut echoed through the lobby. Mr. Manei, who was arranging the cards on the table, said things like “reversed” and “the Tower”, then eventually spoke up.

“If you try hard, you can do it.”

Oof. That was vague.

“Alright, now that Kasumi's fortune telling is over, let's get back to Monopoly!”

Yozuki set a Monopoly board on the table. Apparently the three of them had been playing Monopoly before Mr. Manei's fortune telling session. Yozuki had coincidentally gotten up early for once, but when she went to the lobby, Riria and Mr. Manei were already there playing. And then Yozuki had been drawn into their game.

“But who here brought Monopoly?” I asked. Riria responded “For some reason, it was just here in the lobby. Looks like the hotel's copy. They also have Jenga, Mahjong, Bingo, and even dominoes. Maybe a university domino club spent a night here and forgot it when they left?”

I couldn't help but laugh at her absurd reasoning. “Oh?” Riria glared at me. Then she made a powerful declaration.

“Imma whip yo' ass at Monopoly!”

As we were playing Monopoly, the other guests gradually filtered into the lobby. Miss Meirozaka also came in and began serving drinks. “May we eat yet?” Fenrir asked. “Sorry, but breakfast doesn't start until 8:00.” Miss Meirozaka pointed at the door separating the central and dining buildings. It was the door right next to the table we were sitting at. There was a sign posted reading “Entry prohibited between 11:00 P.M. and 8:00 A.M.” “That's a shame,” Dr. Ishikawa muttered softly.

Eventually, Mitsumura also woke up. When she saw us playing the game, she tilted her head and asked “What are you playing?” “Monopoly,” I said. She hummed.

In the end, the five of us – Mitsumura, me, Yozuki, Riria, and Mr. Manei – all wound up playing together. We played until the time reached 8:00 A.M. Miss Meirozaka removed the sign from the door to the dining building. I clutched my stomach. I was starving, probably because of all the brainpower I'd spent on the game. Mitsumura looked hungry as well.

We opened the door connecting the lobby and the dining hall and stepped through. There was a short hallway, about 20 meters, with a door at the end. We went through the door and entered the dining hall. And we were immediately struck by an uncomfortable feeling.

The breakfast buffet hadn't been left out. And instead of the rich aroma of fresh bread, there was a strong odor of rusty iron. Naturally, we turned our gazes towards the smell. There was a single seat couch that seemed to have been brought from the lobby, and on that couch was a dead body. The victim in this case was Ms. Shihai.

A ten of hearts lay next to the corpse.

Everyone looked at Ms. Shihai's corpse in shock. The chest of her clothes was stained bright red with blood. It appeared she'd been stabbed multiple times with a sharp blade. The murder weapon lay right in front of where she sat. It was an axe with a long handle like a naginata. I thought I remembered its name as a halberd. The halberd had a sharp spear point opposite its axe blade, and it appeared Ms. Shihai had been repeatedly stabbed in the chest with it. The spear-like spike tip jut perpendicularly from the handle. At the sight, Mitsumura started murmuring to herself.

“Why did the culprit kill her using the spear instead of the axe?”

I was the only one close enough to hear the question, and naturally, I had no answer.

Ms. Shihai's corpse was placed against the wall on the south side of the dining hall (the one where the entrance door was located). Her body was seated facing east, towards the door the the dining hall. Also on the south wall, just to the right of the corpse, was a cupboard. The was a faint splatter of blood on the cupboard, about two meters from the corpse.

The murder weapon, the halberd, was lying in front of the couch where Ms. Shihai was sitting, with the end of the handle (the side opposite the spear tip) facing the wall. At the end of the handle was a decorative indigo cloth. It was about the size of a hand towel. When I touched it, it was damp with water. Mitsumura also touched it, then tilted her head to the side.

 

When I actually held it in my hand, the halberd was surprisingly light. It looked like an imitation made for a stage play, and most of the parts were made of plastic. Only the deadly spear had been replaced with a real metal blade. Anyone could have used it.

“So that's why the culprit stabbed her with the spear part,” Mitsumura said. “The axe is fake, so they couldn't have used it.”

After I finished examining the halberd, we turned our attention the the corpse. Dr. Ishikawa and Fenrir proceed with the autopsy.

“The cause of death was stabbing. She was stabbed five times in the chest,” Dr. Ishikawa said.

“The estimated time of death is between one and two hours ago?” Fenrir asked.

“Yes, that matches my findings. In other words, between 6:00 and 7:00 today.”

“I just looked in the kitchen,” said Miss Meirozaka. Even she, who was always so calm, looked a bit shaken up by Ms. Shihai's murder. “Breakfast wasn't ready yet. But Shihai always prepares the food the day before, so there isn't much to do in the morning. She usually starts work between 6:00 and 7:00.”

“So then, it matches the time of death,” Dr. Ishikawa said.

As I listened to them, I organized the information we had in my head. Ms. Shihai came from her room in the west building to the dining hall sometime between 6:00 and 7:00 A.M., where she was killed before she even began preparing breakfast. If you thought about it like that, it matched the time of death. There was no incongruity there. ...No, wait.

There was a massive incongruity.

“Miss Meirozaka,” I said. She turned her head towards me.

“What is it?”

“I'd just like to confirm, there's no back entrance to this dining building, right?”

Miss Meirozaka paused for a moment, unable to understand my intentions.

“...Not just the dining building, the entire hotel doesn't have any rear entrances. All the windows in here are fixed, too.”

The entire north wall of the dining hall was a single large window, but it was an inlaid window that didn't open or close. There was also a window in the corner of the west wall, in the southwest corner, but it was inlaid, too. There was no way anyone could go in or out through it.

“So the only way to get into the dining hall is through the lobby of the central building?”

“Yes, as I said before, there's no way to enter the dining building without going through the lobby.”

I groaned. Then what did this mean? Was this another...

After a moment, Yozuki tugged at my shirt.

“Kasumi, what's wrong?” she asked worriedly. “If you aren't feeling well, it's okay to take a rest.”

“No, it's okay. I was just thinking.”

I looked around at the group. Then, I said “I've realized something important.”

“Something important?” Dr. Ishikawa asked. “What is it?”

“I got up at 5:00 A.M. today.” I woke up early and couldn't get back to sleep. “So I got up and headed for the lobby. There, I saw Yozuki, Riria, and Mr. Manei playing a game, and I decided to join in.”

“Yeah, that's all true,” Riria said. “What's wrong with that?”

“We were playing at the table right next to the only door to the dining hall,” I said. “We started at 5:00, and Riria and the others had been there even longer. A few people occasionally left their seats to go to the bathroom, but I never left my seat. I was there nonstop from 5:00 to when Miss Meirozaka removed the sign from the door to the dining hall at 8:00. During that time, we'd inadvertently wound up guarding the door. And during that time, not a single person went to the dining hall.”

“Do you mean to say,” Fenrir said, “that the dining hall was some sort of locked room?”

“Yes, it's what's called a Broad Locked Room.”

When the number of locked room murders in this country started to increase, the Ministry of Justice released a classification of locked rooms into three different types. Those are “Complete Locked Rooms”, “Incomplete Locked Rooms”, and “Broad Locked Rooms”. Complete and Incomplete Locked Rooms are sometimes combined into “Narrow Locked Rooms”.

The definition of a Complete Locked Room is when a murder occurs indoors and every door and window to the room is locked. This is the most standardized type of locked room.

On the other hand, an Incomplete Locked Room is when a murder occurs indoors and all the doors and windows are inaccessible for other reasons. For example, an inward opening door is barricaded from the inside, or the window was open but no one could enter or exit through it because the room was on too high a floor. Both of these are examples of Incomplete Locked Rooms.

And the definition of Broad Locked Room is any impossible crime that doesn't fit into the category of Complete or Incomplete Locked Rooms. Examples of this include murders with no footprints like you'd see in a classic footprints in the snow mystery, and cases where the entry to the crime scene is monitored by cameras proving nobody used it. However, the line between Broad and mere Incomplete Locked Rooms is ambiguous. For example, suppose a murder takes place in a room with an open window, but the snow outside the window has no footprints, making it impossible for anyone to go in or out. In this case, since the window is open, should we define it as an Incomplete Locked Room since the window was open, or should we call it a Broad Locked Room since it's a variant on the footprints in the snow problem? It's difficult to call, and expert opinion differs.

“Anyway, the scene of the crime, the dining building, was a Broad Locked Room between 5:00 and 8:00 A.M.,” I said. “That means neither the culprit nor the victim, Ms. Shihai, could have gone to the dining building during that time. It's a locked room murder. How did the culprit kill Ms. Shihai?”

“That's...” Dr. Ishikawa thought for a moment. “They must have gone to the dining building before 5:00 A.M., then, right? The dining building was only a Broad Locked Room from 5:00 to 8:00, so if it was before 5:00, then there's no problems. That's how it was done. The criminal called Ms. Shihai to the dining hall before 5:00 A.M. and killed her.”

“But don't you think before 5:00 A.M. is too early to meet with someone? Why would Ms. Shihai have agreed to that? And also, even if Ms. Shihai did go to the dining hall at that time, she was killed at least an hour later, after 6:00. By then, the dining hall had already become a Broad Locked Room, so now we have the problem of the culprit not being able to escape the locked room afterwards.”

When he heard my words, Dr. Ishikawa let out a “Hmm.” Then, Miss Meirozaka joined the conversation. “I don't know how they got out of the dining hall,” she said.

“But I can explain what Shihai was doing in there before 5:00. Like I said, her room is in the west building, but there's also a nap room there in the dining building. When food preparations go on late into the night, she sometimes sleeps in that room instead of going back to her room.”

“And you think she did that yesterday?”

“I think it's pretty likely.”

That would explain why Ms. Shihai was in the dining hall. In that case, the only mystery left would be how the culprit escaped after the crime...

At that moment, an unexpected person spoke up.

“Is that how it is?” said Fenrir, and Dr. Ishikawa, who was intrigued by her mysterious words, asked her

“Miss Fenrir, is something wrong?”

“Ah, no, it's just, well... How do I put this?”

She took a deep breath. Her hair, looking like polished silver, swayed freely.

“I believe I might know who our culprit is.”

“The focal point of this incident is that from 5:00 to 8:00 in the morning today, the only door to the dining hall was being monitored by Mr. Kuzushiro and his friends,” Fenrir said. “So, as already discussed, the dining building was a Broad Locked Room, and during that time, no one, including the criminal, was able to enter or leave the room. Even if the culprit had been hiding in the room ahead of time, they would not have been able to leave after killing Ms. Shihai. However, there is a solution to this conundrum. In fact, I dare say there is only one solution. They could have escaped after the Broad Locked Room was unlocked.”

“They escaped from the dining hall after the Broad Locked Room was unlocked?” I asked.

“Yes, while the door was being monitored, the culprit could not have escaped from the locked room, but that surveillance was lifted at 8:00, correct? At that point, the dining hall was no longer a Broad Locked Room, and the culprit could escape. I'm sure they were hiding under a table and snuck out while we were distracted by the corpse, where they returned to the lobby.”

Indeed, when we were looking at the corpse, our backs were turned to the entrance. If they timed it right, someone certainly could have escaped from the dining hall.

“I see,” I said. I gradually came to understand Fenrir's argument. “In that case, there's only so many people who could have committed the crime. The culprit wasn't able to escape the locked room until after 8:00 A.M. In other words, anyone seen outside the dining hall before 8:00 A.M. can be excluded as a suspect.”

“That's right,” Fenrir said with a nod. Everyone looked at each other and tried to remember. I searched my own memories. Originally, there were twelve people in the hotel. Kanzaki and Ms. Shihai had been killed, and Yashiro had gone down the mountain, so that left us with nine. Among them, who had definitely not been in the dining hall before 8:00 A.M.?

“First of all, there's me,” I said. “I was in the lobby before 8:00 A.M. Yozuki, Riria, and Mr. Manei were playing games with me. We're all safe.”

That had already stricken out four suspects. Now there were only five left.

“I was in the lobby, too,” Miss Meirozaka said. “I was serving drinks.”

That was true. Now there were four.

“I was also in the lobby,” said Mitsumura. “I joined the monopoly game halfway through.”

Also correct. Only three.

“I was there, too,” said Dr. Ishikawa, and Fenrir raised her hand and said “Myself as well.” ...My memory on those two was vaguer. I felt like they were there, but I also felt like they weren't.

“I'm sure they were both in the lobby,” Mitsumura said. “I remember them.”

“Is that so?”

Well in that case, there was only one suspect left. And that was...

“Mr. Sagurioka?”

Saying that, I took a look around. That was when I noticed.

“Come to think of it, where is Mr. Sagurioka?”

I couldn't see him. Or rather, had I seen him at all that day?

“I haven't seen him either,” Yozuki said. “Me neither,” said Riria. Several other people also announced that they hadn't seen him. No one in the room said they had.

“Then that means...”

I turned to look at Fenrir. She nodded in response.

“The only person able to commit this crime is Mr. Sagurioka. In other words, Mr. Sagurioka killed Ms. Shihai.”

I didn't want to believe it. But it made sense. In that case, we had to find him as soon as possible.

“Mr. Sagurioka's room is on the first floor of the east building,” Miss Meirozaka said. “Let's go. He might still be there.”

Dr. Ishikawa, Fenrir, and Mr. Manei left the dining hall, following Miss Meirozaka. Yozuki and Mitsumura followed suit, and I followed after them. As we went down the 20 meter hallway connecting the dining hall and the central building, I heard a grieving voice from behind me. When I turned around, I saw Riria in tears.

She held her head in her hands.

“...I hate this. I wanna go home.”

I couldn't agree more.

The first floor of the east building had no carpet, exposing the amber wood of the floor. We quickly crossed the floor to Sagurioka's room. Sagurioka's room was in the middle of the first floor. When we arrived at the room, we were speechless to a one. A seven of hearts playing card was stuck to the door.

“No way, Mr. Sagurioka, too?” Yozuki said in dismay. When Miss Meirozaka grabbed the knob and tried to open the door, we heard the sound of the deadbolt (that's the bolt that sticks out the side of the door when it's locked) hitting the frame echo through the hall.

“It's locked,” Miss Meirozaka said. I knocked on the door several times. “Mr Sagurioka? Mr. Sagurioka, are you there?”

“He's not responding,” Dr. Ishikawa said. “As I thought, he's already...”

“What do we do? Should we break it down again?” Mr. Manei suggested. Miss Meirozaka thought about it for a moment, then shook her head.

“Let's go out in the garden and look through the window. We're on the first floor, so we might be able to see what's going on in there first.”

We all nodded and returned to the lobby in the central building. Then we went out the front door. We ran through the snow-covered garden and made for the window of Sagurioka's room. Then, everyone pressed their faces right up against it and looked into the room.

A man was lying there. It was Sagurioka. There was a pool of blood on a floor the same bright color as the hallway.

We decided to break the window to get into the room. I got a mop from inside and jabbed the tip of the handle into the glass until it broke. After breaking open a space large enough for everyone to get in, we climbed through the window frame and entered Sagurioka's room. Dr. Ishikawa and I approached Sagurioka, who was still lying on the floor. I immediately realized it was too late.

Sagurioka had been shot in the forehead with a handgun. He was still in his pajamas, and one of the buttons on the top was undone, probably due to a struggle with his killer. There was an empty cartridge on the floor, so he'd probably been killed with a semi-automatic pistol. Revolvers don't ejected their spent cartridges automatically, so it probably wouldn't have left one at the scene.

I nodded and turned to Miss Meirozaka.

“How's the soundproofing in this room?”

“I'm told is pretty good,” she replied. “This was originally Byakuya Yukishiro's audio room. So even if a gunshot were fired inside the room, I don't think the noise would have made it outside.”

In the face of Miss Meirozaka's explanation, all I could say was “I see.” That meant we couldn't narrow down the time of death based on when the gunshot was heard. It was unclear whether the culprit knew in advance that this room was soundproofed, but I thought I remembered Sagurioka telling me that he'd visited this hotel for a magazine interview. In that case, it was highly likely that the person who'd made the reservation for him was the reporter from that magazine. And if that reporter was actually the culprit pretending to be a reporter, they could have easily made Sagurioka stay in this room. All they would have had to do was specifically request room whatever in the east building while making the reservation.

As if interrupting my thoughts, I heard an “Ah” from someone else. It was Yozuki. She was standing in front of the LCD TV in the room, pointing at the pedestal it was mounted on.

“The key.”

A key was right where she was pointing.

“That's the key to this room,” said Miss Meirozaka as she picked it up. “The room number is stamped right on it.”

I nodded, looked around at the others, then spoke.

“Before Yozuki approached that TV stand, did anyone else go near it other than her?”

Everyone shook their heads. Yozuki looked confused and said “Why do you ask?” “No reason,” went my vague reply. I had thought that maybe someone had left that key on the TV stand in the chaos of the initial body discovery. But if nobody approached the TV stand, then nobody had the chance. In other words, that key hadn't moved since before we entered the room.

After drawing that conclusion, I approached the door, which was the only entrance to the room. No one had approached it since we went inside, either. But the door was indeed locked from the inside.

“A locked room?”

The door was locked and the window was fixed and didn't open. And the only key was found inside the room.

“It's a Complete Locked Room,” said Fenrir. Then she approached the door herself and looked at the bottom. “And there's no gap under this door. This is a more solid locked room than the one where Mr. Kanzaki was killed.”

It was as she said, there was no gap under the door. That meant the method of returning the key under the door wouldn't work.

Fenrir stroked her silver hair and turned her eyes towards Dr. Ishikawa.

“Dr. Ishikawa, shall we begin the autopsy? We might uncover something interesting.”

“Will we now?” Dr. Ishikawa asked, tilting his head.

“We might. Depending on the estimated time of death...”

Fenrir said that and began to examine Sagurioka's body. After she'd finished her autopsy, Dr. Ishikawa replaced her. They both gave the estimated time of death as between 2:00 and 3:00 A.M. today. That was when I realized what Fenrir's earlier comment had meant.

“Is that so?” I whispered. When Yozuki heard me, she got curious and asked “What is it?” I told her... and everyone else, too.

“Ms. Shihai's estimated time of death was between 6:00 and 7:00 A.M. today. If Mr. Sagurioka had already been killed before 3:00 A.M., there's no way he could have killed Ms. Shihai.”

“But then,” Yozuki said, “does that mean someone else killed Ms. Shihai?”

“But isn't that weird?” Riria asked with a tilt of her head. “Mr. Sagurioka was the only one who could have killed Ms. Shihai, right? If he isn't the culprit, than who could it have been?”

Riria was completely right. The dining room building was an enormous locked room, and we'd all been seen outside of it.

“The Broad Locked Room has been restored,” Fenrir said happily, “and this room where Mr. Sagurioka was killed is also a perfect locked room. It's wonderful, seeing two locked room murders happen in one night. I'm so glad I came to this hotel.”

She was so happy she was faintly blushing. Then she pulled out her smartphone and started taking pictures. I instinctively grabbed her arm. “Eek!” Fenrir cried. And the next moment, I was floating in midair. It wasn't until after my back hit the floor that I realized I'd been thrown.

“Kasumi, are you okay?” Yozuki was rubbing my back. “You were hit with a beautiful throw,” Mitsumura said with concern(?).

Fenrir, the one who'd thrown me, turned away on the spot. It seemed she had no intention of apologizing.

I groaned as I got up off the floor and decided to try and make sense of all this. Two different locked rooms had been created, and Ms. Shihai and Sagurioka had died in them. Eventually, I decided to start with the room where Ms. Shihai was killed. So I decided to ask Dr. Ishikawa.

“Is it possible that Ms. Shihai's estimated time of death is wrong?”

The only thing keeping the scene a locked room was her time of death being during the window when the door between the lobby and the dining building was being monitored. If Ms. Shihai had actually been killed before the post at the door was set, then the crime scene would no longer be a locked room.

“I was just thinking the same thing,” said Dr. Ishikawa. “But I don't think there was any mistake in the autopsy. And Miss Fenrir got the same result I did.”

“But it's possible you both made a mistake.”

Ishikawa “Hmm”ed in thought. Then he shrugged.

“Then why don't we double check? I think that will put everyone's minds at ease, and to be honest, I'm starting to second guess myself as well.”

We all returned to the dining hall and examined Ms. Shihai's body again. Dr. Ishikawa, who performed the autopsy, eventually looked up and gave us a strained smile.

“No change. As I thought, the time of death was definitely between 6:00 and 7:00 this morning.”

That confirmed that the scene was a Broad Locked Room. I frowned. I groaned. In the three days since we'd arrived at this hotel, three locked room murders had occurred. Even if we lived in an era where locked rooms were common, that was too many.

“Dr. Ishikawa, may I also take a look at Shihai's body?”

It was Miss Meirozaka. Dr. Ishikawa tilted his head at her.

“Of course, but why?”

“Just give me a minute.”

Miss Meirozaka crouched down next to the corpse. Then she touched Ms. Shihai's body. Eventually, she found it, and pulled something from her inner pocket.

It was a key.

“This is the master key to the west building,” she said.

Come to think of it, unlike the east building where Kanzaki and Sagurioka were killed, the west building did have a master key.

“I'll hold onto this. There's only one master key, so if we lost it, it'll be trouble,” Miss Meirozaka said, putting the master key in her pocket. Then, just as she was about to stand up, she stopped.

“Huh?” She arched her neck. “Something fell out. Is that an envelope?”

Miss Meirozaka's gaze was directed to the bottom of a table about five meters from the corpse. There was, in fact, an envelope lying there. We hadn't noticed it before now because it lay in the shadow of the tablecloth.

I approached the table, bent down, and picked up the envelope. It was a plain white envelope with nothing written on it. Inside was a folded piece of paper.

I took it out and looked through it.

It was Ms. Shihai's suicide note and a confession to the murders.

This is a summary of Ms. Shihai's final message. She was the culprit of the Playing Card Serial Murder Case. She was also the one who killed Kanzaki and Sagurioka. She regretted her sins and chose to atone with death, and so on and so on. The suicide note had been written on a computer, but at the bottom was a handwritten signature in the name of “Reiko Shihai”.

“It's Shihai's handwriting, no doubt about it,” said Miss Meirozaka after checking the note. Then she shook her head in confusion. “Still, I can't believe it. Shihai was the culprit?”

“It is a shock,” said Mr. Manei. “And she committed suicide on top of it all. Wasn't she stabbed to death with that halberd's spear?”

“I think so,” Ishikawa shrugged. “But that's not proof it was murder. For example, if she held the handle near the spear point, she could have stabbed herself with it. But the handle is so long, it wouldn't be easy.”

Indeed, the handle of the halberd was about two meters long, which seemed too long for a suicide by self-stabbing. The halberd appeared to be able to be disassembled for ease of transport, so if I were going to commit suicide with it, I would have definitely wanted to shorten the handle first.

“But in the end, it is a suicide, right?” Riria asked. “The crime scene was a perfect locked room, and we even found a suicide note with a handwritten signature. If this wasn't a suicide, then how did the culprit kill Ms. Shihai, and how did they prepare this note?”

Her words cast a deathly silence over the room. But eventually... “Maybe you're right.” Miss Meirozaka spoke up.

“It's a bad ending, but we have no choice but to accept it. Everyone, I'm sorry Shihai caused you all so much trouble.”

Grasping the hem of her maid apron in both hands, Miss Meirozaka gave us all a deep bow. The atmosphere was stifling. Riria said “N-No, you don't have to apologize to us, Miss Meirozaka” in a panic.

Someone tugged on my arm. It was Yozuki, and she spoke to me with a frown as she flapped her collar.

“...Hey, isn't this room a bit too hot?”

Now that she pointed it out, it did feel like the temperature in this room was really high. It felt like a hazy day in midsummer. Did they have the heating on too high?

“Um, where's the remote for the heating?” Yozuki looked around the dining hall. Eventually, she found it and ran to it. The remote had been placed on a table by the window on the north side of the dining hall. When Yozuki held the remote, she exclaimed “Huh?”

“The temperature is set to normal. Why is it so hot?”

The handgun used to kill Sagurioka was found in Ms. Shihai's room. It was a semi-automatic pistol with no silencer. Just in case, we decided to keep the pistol and magazine separate, so Miss Meirozaka took the magazine and, for some reason, Riria took the pistol. “There's no one here I trust more than me,” according to her. Mr. Manei begged her, “No, Miss Riria, it's dangerous. Let someone else take care of it,” but Riria stubbornly repeated “It's 'cause there's no one I trust more than me” until he gave up.

Everyone looked a bit relieved that the case had ended after Ms. Shihai's suicide. Miss Meirozaka made a simple breakfast, and after eating, we all returned to our rooms one by one. I also returned to my room and sat thinking, only leaving for lunch and dinner. But after taking my bath, I suddenly thought of something and decided to go back to Sagurioka's room. Even though the case itself was solved by the culprit's suicide, there were still aspects that had been left unresolved. The locked room at the scene of Sagurioka's murder... and also the meaning of the playing cards left at the scene. The three murders of the Playing Card Serial Murder Case took place five years ago – and if you included Ms. Shihai's suicide, there were three cases here, as well. There were six cases total. The playing cards found at the scenes were all of the suit of hearts, but their numbers were all different, and I wondered if that had any meaning.

In the Playing Card Serial Murder Case of five years ago, the first case, of the former detective, had a six of hearts left at the scene. When the Chinese man was killed in the next incident, a five of hearts was left – and when the president of the black company was poisoned in the third case, a four of hearts was left behind, after which the Playing Card Serial Murder Case went into hibernation for several years.

Then, another incident occurred here in this mansion, where Kanzaki was killed and an ace of hearts was left behind. Then a ten of hearts was found at the scene of Ms. Shihai's suicide. The playing card we found at the scene of Sagurioka's murder was a seven of hearts. Ms. Shihai's note didn't say anything about the meaning of those numbers. Like the mystery of this locked room, they remained unsolved. Was it some sort of code? Or did it hint at an unknown connection between the victims, a missing link?

I fiddled with my hair.

I looked again at where Sagurioka's dead body had once been. The corpse itself had already been taken away, stored in the wine cellar of the dining building to preserve it for the authorities. In its place had been drawn a white humanoid outline in nylon string. Sagurioka had been lying next to the wall, with his legs thrown against it. There were only 15 cm between his feet and the wall. His hands were spread, parallel to the wall. There was a nightlight on the wall, where Sagurioka's feet pointed. It must have been on when the crime was discovered. However, it wasn't that bright, and in the light, it was hard to see unless you were right in front of it.

I decided to investigate the wall opposite the one with the nightlight. There was a bullet hole and a blood stain. They were both behind the fallen Sagurioka. It appeared the bullet had sank into the wall without penetrating all the way through. It had probably lost energy when it penetrated Sagurioka's skull.

“I'm flabbergasted. Just what are you doing here?”

When I turned towards the voice, I saw Mitsumura standing in the entrance to the room. I shrugged my shoulders.

“It's exactly as it looks. I'm investigating the locked room.”

“The case is already solved.”

“Yeah, but I'm still curious. I'm the type who gets curious when there's a mystery in front of me I can't solve.”

“'Oh, I get so curious when there's a mystery I can't solve', you're such a show-off,” Mitsumura said dismissively. “That just means your life is full of curiosity.”

“I think it's a great way to live.”

“It's greatly unrewarding. It just means you're constantly faced with trials you aren't good enough for.”

She was being harsher than usual. Even though she was frowning, I tried to cheer her up.

“But that's okay, because I have friends I can rely on.”

Mitsumura looked shocked. “Friends?” she said. I pointed at her. “Yep, friends,” I told my friend.

“That's why I want to ask for your help in solving this locked room murder.”

Suddenly, she frowned. And she spoke in a morose voice.

“Are you trying to drag me back into the case?”

“No matter what I do, you're already involved. You're inside the closed circle.”

“And what's wrong with that?” Mitsumura looked at me with one eyebrow raised. “You're always trying to make other people solve your problems for you. Don't you ever want to try solving a problem yourself?”

“Too bad, but I'm the type who looks up the answer as soon as I get stuck.”

“Typical. You're the type I hate the most.”

“You say that, but don't you just lack confidence? You think this locked room might be too much for you.”

I could see for a moment that I'd gotten to her. She glared at me and said

“Are you provoking me?”

“Yeah.”

“Do I looked like the sort of shallow woman who'd rise to any challenge?”

“Yeah.”

“Well too bad for you, but I'm a grown up now. I'm not interested in being a detective clown who gets carried away all the time.”

I didn't know what a “detective clown” was, but the mental image it summoned was horrifying.

Mitsumura sighed. And she spoke calmly.

“But it would be annoying if people believed I couldn't solve this mystery, so I'll accept your challenge.”

You took it immediately! You haven't grown up at all!

She ignored my feelings and looked around the room. Then, her eyes fell on the white outline of Sagurioka's body.

“Mr. Sagurioka's corpse was throwing its legs against the wall.”

“Uh-huh.”

“The distance between his feet and the wall was about 15 cm.”

“Yeah.”

“There was an empty shell casing on the floor.”

“That's right.”

“And a nightlight on the wall.”

“That there was.”

“I'm sure this light was on when Mr. Sagurioka's body was found. That means it was also on at the time of the crime.”

After saying that, Mitsumura turned on her heel and moved to the opposite wall. She stared at it.

“The bullet is still in the wall.”

“...Yes? Obviously.”

“Whether we take that fact for granted or not may be the deciding factor in solving this case.”

She ran a hand through her long black hair. And she spoke to me.

“I suppose that's it. It looks like there wasn't that much of a trick used.”

My eyes went wide.

“You solved it already?”

“Yes.”

“Isn't that a bit too fast?”

“It's standard speed for me, though for you, it may as well be the speed of light.”

It definitely was. She was a detective clown moving at light speed.

“In that case, I'd wager that...” Mitsumura knelt down on the floor and looked under the bed. Then she reached her hand into the gap and said “I knew it.”

“This is what I've found.”

The object she proudly displayed was a small, threadbare button.

“What's that button?”

“Isn't it the one missing from Mr. Sagurioka's pajamas?” Mitsumura asked. “Look, one of his buttons was undone, right? It was probably that one.”

“So, when Mr. Sagurioka got into a struggle with his killer, the button was torn off and rolled under the bed?”

“Well, what do you think?”

Mitsumura gave a meaningful shrug. I was getting impatient.

“So what was the trick?”

“You want me to tell you?”

She was acting very out of character. A small smile appeared on her lips.

“Don't worry, I'll explain everything. I'll lay things out using logic... simple logic.”

“There were many clues left at the scene,” Mitsumura said. “By combining these hints, the trick will emerge before us.”

Her theatrical delivery bothered me. I objected strenuously.

“Please get to the point, detective clown.”

“Who's a detective clown!? ...But alright then, I'll explain in a way that even Kuzushiro, who once failed every question on the IQ test, can understand.”

She casually made up a new black mark on my record. Well, that was fine.

“So, what are the clues?”

“The first is that Mr. Sagurioka threw his legs towards the wall when he died. The distance between his feet and the wall was only 15 cm.”

“Ah, come to think of it, you mentioned that earlier.”

“Yes, I did. ...So, what does this hint mean? Clearly, it means that Mr. Sagurioka was shot very close to the wall.”

“Hmm...”

I turned my attention towards the white outline marking where the corpse had been found. I thought that worked out.

“Well, that much is obvious.”

“Yes, it's obvious. But if you combine it with the next clue, it reveals something interesting.”

Mitsumura pointed at the wall opposite the nightlight, which was also opposite the wall where Sagurioka had thrown his legs.

“The bullet that hit Mr. Sagurioka was stuck in that wall,” she said. “Do you know what that means?”

I tilted my head. Honestly, I didn't. All I could tell was which way the bullet came from.

I told that to Mitsumura. And she responded with a surprising answer.

“Yes, you can tell which way the bullet came from. And if you know that, you can recognize the great contradiction in this locked room.”

“Great contradiction?”

I looked around the room. I didn't notice any contradiction. Apparently my contradiction radar was busted.

“So, it's like this: Do you have anything to write with?”

As Mitsumura looked around, I took out a pen and notepad from my pocket and handed them to her. Mitsumura drew a simple diagram. Specifically, this one:

“Their positional relationship must have been like this.”

“That's a really simple diagram.”

“I'm quite the artist, aren't I?” she said with some pride. “In other words, if you think about it normally, it would have been like this: The culprit used their handgun to shoot Mr. Sagurioka while standing with their back to the wall with the nightlight, causing the bullet to get stuck in the opposite wall.”

I groaned.

“Isn't that also obvious?”

“No, it isn't obvious at all. Because the culprit shooting Mr. Sagurioka with their back to the wall is absolutely impossible.”

Those words make me feel very strange. Absolutely impossible? Why would it be impossible? The culprit, with their back to the wall, pointed their gun at Sagurioka and pulled the trigger. That's all there was to it, and I didn't see any reason it couldn't be done.

“They couldn't do it. And this is why.” Mitsumura moved closer to the wall and gently leaned against it. Then she mimed holding a pistol. “Basically, if you want to shoot someone with your back to the wall, you have to stand between the wall and your target.”

She pointed her invisible gun at me.

“Then, Kuzushiro, would you please come closer?”

With her “gun” still pointed at me, I did as I was told and approached Mitsumura. I stopped about three paces away from her.

“No, come closer.”

I took two more steps. Mitsumura said “Closer.”

I gave her a confused look.

“Just how close do I need to be?”

And then she laughed at me.

“Maybe... about 15 centimeters from the wall?”

Don't be ridiculous.

If I got that close, I'd bump into her. No, it would be more like I'd be crushing her against the wall. To begin with, a human body is thicker than 15 cm. As long as she was there, it was impossible for me to get within 15 cm of the wall.

“Ah!”

I finally realized what Mitsumura was trying to say.

“You mean...?”

“Yes, that's it,” she said. “Mr. Sagurioka was lying 15 cm away from the wall. So if the culprit had shot Mr. Sagurioka, they would have had to squeeze into the 15 cm gap between the wall and Mr. Sagurioka. But that's clearly impossible, right? Which means, it's impossible that the culprit shot Mr. Sagurioka with their back to the wall.”

I nodded. But at the same time, that raised further questions. If the culprit couldn't have shot and killed Sagurioka with their back to the wall, then how had they killed him?

That's when I realized something.

“Maybe they shot from the next room?”

A bullet fired by the culprit in the next room penetrated the wall and hit Sagurioka in the head. That would allow the culprit to shoot the victim while they were close to the wall without having to crawl into the small gap between the victim and the wall.

“But...” Mitsumura turned her gaze to the wall Sagurioka's legs pointed at. “There aren't any bullet holes anywhere in the wall.”

“I feel pathetic when you shoot it down that quickly.”

“You are pathetic.”

“But then, how is it possible?”

I was left scratching my head. It was impossible for the culprit to be between the wall and the victim. It was equally impossible for them to shoot from behind the wall. That made it seem like it was impossible for the culprit to shoot Sagurioka at all.

When I told that to Mitsumura...

“Well then I guess that's how it is,” she said. “As you say, it was impossible for the culprit to have shot and killed Mr. Sagurioka with a pistol. Therefore, the only possibility is that the culprit didn't shoot and kill Mr. Sagurioka with a pistol.”

I was stunned silent. No, that wasn't possible. Because Sagurioka really was shot.

“Is that so?” she laughed. “Was Mr. Sagurioka really shot in the head with a pistol? Is there no other way they could have gotten a bullet through his head without using a gun?”

I racked my brain for a while, and then it hit me. “No way.”

Mitsumura nodded.

“There's only one possibility. The bullet went off and pierced Mr. Sagurioka's head due to a trick the culprit set up. One that caused the bullet to go flying out of nowhere.”

“An exploding bullet trick?”

Mitsumura nodded at me. “I can think of many possibilities,” she said, holding up her index finger.

“For example, maybe they used yellow phosphorus?”

“Yellow phosphorus?”

“Yes, yellow phosphorus has the property of igniting when it reacts with air, so it's usually stored in water, right? So you can take advantage of that property to make a timed ignition device. For example, if you wet a small amount of yellow phosphorus, wrap it in wet cotton, and put it in a 1 cm square plastic bag with a desiccant, then over time, the water in the cotton will evaporate and the yellow phosphorus will catch fire when it's exposed to air. In other words, it will create a spark on a timer. Then, if you put that spark inside a bullet cartridge, when the time comes, the spark will ignite, burning the gunpowder inside the cartridge and causing the bullet to explode.”

I imagined the mechanism Mitsumura had described in my mind's eye. A special bullet that could be fired without the use of a gun. A booby trap like that could completely explain the solution to this locked room. Why had Sagurioka been shot to death inside a locked room? Because he himself had locked the room, and in that room, he'd been felled by his killer's bullet.

I felt the fog over my eyes suddenly lift.

But at the same time, I couldn't help the feeling that there was something wrong with her logic. I felt like there was a problem there I couldn't overcome. So I asked her about it. 

“Is that trick really possible?”

Mitsumura shrugged her shoulders and said “What do you mean?” “It's a matter of probability,” I replied.

“Mr. Sagurioka was shot in the head. However, since they used a timed ignition device based on yellow phosphorus, the culprit couldn't have known the exact moment the bullet would go off, right? But the culprit did shoot Mr. Sagurioka in the head. They couldn't have done that if they didn't know when the bullet would go off, and they needed some way to lead Mr. Sagurioka near the wall where the bullet was placed.”

But that was flatly impossible. Which meant that the entire trick was impossible.

However, Mitsumura didn't seem particularly upset, and she simply replied “Yes, you're right. So perhaps we have it backwards.”

“Backwards?”

“Yes, backwards. The criminal didn't know the exact time the bullet would go off. That's why the bullet hit Mr. Sagurioka in the head.”

I frowned. Was this some kind of Zen riddle?

“What do you mean?”

“The clue is the button that fell under the bed.”

“The button?”

“Perhaps the culprit placed the bullet under the bed,” Mitsumura said, “facing upright. The cylindrical bullet could have stood perpendicular to the floor. The only thing left to do was to add the correct amount of moisture to the absorbent cotton wrapped around the yellow phosphorus. If they adjusted it so that the bullet would fire at some point during the night, the bullet would pass through the bed and hit Mr. Sagurioka in the back while he slept. A gunless bullet wouldn't fly straight, but it couldn't have missed at a range of only tens of centimeters. The killer had imagined a perfect trick, but something they hadn't anticipated happened, and Mr. Sagurioka died in an unexpected way.”

“Something they didn't expect?” I tilted my head.

“Yes, Mr. Sagurioka lost a button off his pajamas.” Mitsumura showed be the button she'd picked up from under the bed earlier. “Mr. Sagurioka probably got out of bed in the middle of the night to use the bathroom or something like that. At that time, the button from his pajama top, which was likely already frayed and coming off, fell to the floor. He looked under the bed to find the button, and there he saw the bullet meant to kill him, sitting on the floor.”

I imagined the scene. I'm sure Sagurioka would have forgotten about the button and immediately reached for the bullet.

“But since it was night and the lights in the room were off,” Mitsumura said, “the room was dark, even with the nightlight. Therefore, Mr. Sagurioka had no idea what the object he'd just picked up was. All he knew was its vague shape. Mr. Sagurioka approached the nightlight on the wall to get a better look. However, the nightlight wasn't very bright, and he couldn't see by it unless he got within 15 cm of it and held the bullet directly up to the light. And then, a most unfortunate coincidence occurred. Just as Mr. Sagurioka held the bullet up to the light, it exploded and pierced his head.”

And as a result, Sagurioka had been shot not in his bed, but against the wall. That made it impossible to believe he'd been shot by the culprit with a pistol, giving Mitsumura the opportunity to realize the truth behind the trick.

“So, according to the culprit's original plan, the empty shell casing was supposed to have been found under the bed. That would have made it look like someone hiding under the bed had shot Mr. Sagurioka in his sleep.”

However, due to a series of coincidences, that result had changed.

I groaned. It was true, Mitsumura's theory did explain everything found at the scene.

Honestly, I was convinced, but at the same time, I had some more questions. So I went through them, one by one.

The first thing that caught my attention was...

“When did the culprit put the bullet under the bed?” I asked her. Mitsumura put a hand on her chin, then replied “Well, I don't know the exact time.”

“They must have persuaded Mr. Sagurioka to let them into his room at some point. It may have been last night, or the day before. However, due to the nature of the trick, it would have been better for them to plant the bullet as close to the time of the crime as possible, which would make it easier for them to predict the time the yellow phosphorus would ignite. Therefore, it is more natural to assume that the bullet was planted last night.”

I nodded at her answer. Certainly, creating a bullet that would explode after 3 hours was easier than creating a bullet that would explode after 30. In that case, as Mitsumura said, it seemed safe to assume that the culprit had visited Sagurioka's room last night and planted the bullet then.

That explained, I asked another question. “Okay, next question.”

“What about the issue of the ballistic markings? There are marks left on a bullet when it comes in contact with the rifling of a gun's barrel as it passes through. In the trick you've described, the bullet that killed Mr. Sagurioka wasn't fired from a handgun, so there wouldn't be any ballistic markings left. Won't the police realize the trick as soon as they investigate the bullet?”

Mitsumura answered my question with a shrug and a “Is that all?” And as though she had her answer prepared in advance, she immediately started talking.

“It isn't that big a problem, is it? All they had to do was recycle a used bullet that already had ballistic markings on it. The cartridge was used already, too. I checked, and there was a mark on the detonator where it was hit with the hammer.”

I didn't know much about that, so I just kinda said “Ah, I see.” I didn't see any problems there. This light speed detective clown girl was also a debate champ. Maybe she was less of a light speed detective clown and more of a light speed mass debating clown.

“But with that trick, there would be traces of yellow phosphorus left on the shell casing at the scene, right?” I said. “If the police investigate that later, they'll probably see through the trick.”

“They wouldn't investigate the contents of the cartridge,” came Mitsumura's immediate reply. “They wouldn't think to do a chemical analysis like that unless they already knew the trick and were working backwards. There's also the possibility that the culprit is planning to seize an opportunity later to replace the shell casing with one that doesn't contain yellow phosphorus. It's a closed circle, and there's still plenty of time before the police arrive.”

When she put it like that, it sounded like there was almost no risk that they would ever find traces of yellow phosphorus on the cartridge. I was impressed. She'd already managed to answer almost all of my questions. Only one remained, so I asked it.

“One last question, how did the culprit manage to bring the special bullet into the hotel? It would be dangerous to carry around something like that, not knowing when it would go off.”

Mitsumura answered immediately.

“I suppose they must have assembled it inside the hotel.”

“Inside the hotel?”

“Yes, bring the bullet and the casing as separate pieces. That way, they wouldn't have had to carry around an armed yellow phosphorus bullet, right? They wouldn't have had to sit on the train, worrying if it would go off. Well, if Ms. Shihai really were the culprit, there would be no need to go outside with the bullet at all, so there would be no need to worry about it going off.”

I noticed Mitsumura's statement just now had some interesting word choice.

“'If' Ms. Shihai were the culprit? You think she isn't?”

When I said that, Mitsumura made a face that clearly communicated disappointment. Apparently that was a mistake.

“I mean, she isn't, is she? When the culprit commits suicide inside a closed circle, that means they aren't the real culprit, but someone the actual culprit killed and made to take the fall. Isn't that how it works in most mystery novels?”

That was certainly true. The thought had occurred to me too, but...

“But Ms. Shihai left behind a suicide note.”

A suicide note with a handwritten signature. That was why I couldn't shake the belief that she really had committed suicide.

“That's no problem.” Mitsumura shot me down at once. “For example, on top of the printed suicide note, they layered another piece of paper with Ms. Shihai's handwritten signature, like a note or a letter she'd written in the past. They firmly traced Ms. Shihai's signature with a ballpoint pen. Then, the pressure of the writing would make leave an indentation of the signature on the suicide note below, right? All they had to do was trace the indentations with their pen. That would let them leave a signature that appeared to be left in Ms. Shihai's handwriting on the suicide note. Although it's possible a detailed scientific investigation would be able to reveal the forgery, it would be impossible to detect with the naked eye.”

Her smoothly flowing explanations were extremely impressive. It would be completely possible to forge a signature using that method. However, that also destroyed the only remaining defense of the idea that Ms. Shihai had committed suicide, meaning the real culprit was still alive.

In other words, there was still a murderer lurking...

“No, I'm sure it's over.” Mitsumura assuaged my doubts. “No more murders will happen in this hotel. I don't know who the real culprit is, but they wouldn't have left a fake suicide note blaming Ms. Shihai if their plan weren't finished yet. No one here is dumb enough to do something like that, there'd be no point.”

That made sense to me.

Mitsumura gave me a small smile and said “Then it's about time for a break. Good night, Kuzushiro.”

I thought to myself as I waved at her back. Even I didn't expect she'd solve it that easily.

As expected, she was an expert on locked rooms. As a detective or as a criminal.

The next morning, I woke up to the sound of a knock on the door. It was only 7:00 A.M. When I opened the door, I saw Fenrir standing there.

“I'm sorry I threw you yesterday.”

That was the first thing she said. “Oh,” I muttered. “It's fine, I'm over it.” ...Actually, it hurt like hell. But I'm not the sort of guy who lingers on being rejected by a girl. Fenrir and I decided to make up there.

I scratched my head.

“Did you come all the way this early in the morning just to tell me that?”

“No, Mr. Kuzushiro, the reason I visited you is something entirely different,” Fenrir said. And then she told me “I was out on my morning walk when I discovered a body.”

A... A body?

I found that very confusing.

Mitsumura had been so sure there wouldn't be any more murders.

But the silver haired girl before me spoke in a voice as clear as a bell.

“Mr. Manei was murdered. In a locked room, of course.”

 

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