Finally moving away from short stories!
Of course, that is until in the early morning, they are forcefully awakened by an earthquake. While fortunately, only one of them is lightly hurt by hitting her head, they soon learn they are in a desperate situation: the large rock which had been sitting in front of the steel door leading back to the ladder has been moved by the earthquake, blocking the door! When they go to the second basement floor beneath the entrance and the rock, they find the rock is actually attached to a pulley system, which can be operated by turning a wheel in that room: Shoutarou suspects this was a security measure of the Ark's original users. In times of trouble, they could use the pulley system to first pull the rock towards the door to barricade themselves. Closer examination of the system shows they can actually pull the rock through a hole down to the second basement floor: this was probably designed like that so if the first door was breached, they could pull the rock down one floor below and then block the door to this room, where theres's not only the pulley system, but also the ladder leading down the currently flooded third basement floor. But because the pulley system has to be operated manually, this means the person turning the wheel will be locked up in this room, as the rock will then block this door. But not only is the third basement floor now flooded, the earthquake has caused the water level to slowly rise, and in just about a week, more of the second basement floor will be flooded, which will render the pulley system unusable. This means one of the ten people here shall have to "sacrifice" themselves to save the others: they will have to operate the wheel and pull the rock down to the second basement floor, opening the steel door outside, but locking themselves in the room below. But not only is the water level rising, due to the isolated location of this base, the fact they don't know exactly where they are and there's no phone signal, and it's unclear how long it'll take them to make it back to the civilized world because who knows what the earthquake has caused or whether new earthquakes will occur, it is not certain that the others will be able to get help in time for the person left behind. It is during this stressful time one of them ends up dead: Yuuya is found strangled in one of the rooms while they were all looking for tools that might be useful. Nobody understands why Yuuya was murdered, but they realize that if there's one person who should sacrifice themselves and put themselves in danger in order to save the others, it's the person who just killed someone. But can they figure out who the murderer is in time while imprisoned in this underground base, and can they convince the murderer to repent for the murder and help the others? The deadline is about one week, but the clock is ticking faster and faster in Yuuki Haruo's Hakobune ("The Ark", 2022).
I have never read anything by Yuuki before, but Hakobune caught my attention because it managed to rank into the various major best mystery book rankings for books released in 2022 (technically late 2021 - late 2022), taking first place in Bunshun's Mystery Best 10, second place in the Honkaku Mystery Best 10 and fourth place in Kono Mystery ga Sugoi 2023 among others. The description also sounded interesting, with an underground closed circle situation and the people being forced to find the murderer because they need them to sacrifice themselves to save the others. I also happened to catch people saying here and there the logic behind the solution of the mystery was memorable, and as a big fan of logic-focused mystery stories, I of course had to read this.
So I went in with pretty high expectations, and yeah, I was not disappointed! Though I have to say, this was also because I had heard people saying that you had to be prepared for a very artificial closed circle situation, a very forced way to put the characters in their specific predicement and that's really true. You can easily tell that the whole deal with the underground complex, and especially how the pulley system is set-up with a rock and how the one operating it will have to stay in that room with a rising water level is all just there to put the characters in a very desperate situation, but at no time does it ever feel really natural. Of course, mystery fiction is often incredibly artificial, and not seldom, the curious locations or characters just scream out loud they only exist to faciliate a specific mystery plot, but in the case of Hakobune, I have to say the Ark really feels like one big plot device. You don't really learn much about the Ark itself throughout the book, only that it exists and theories about why it is built the way it is. Also: the dimensions of the Ark are a bit wacky. The whole thing is built inside a natural cave, but still, it's an underground complex with corridors, stairways and rooms (with working electricity), so it can't be that spacious, and yet people can wander around the complex without others really noticing them or hearing them walking around, which is really weird. More murders occur in the book besides the initial one with Yuuya, but while you could argue the Yuuya murder was feasible because nobody expected people to be murdered and they were walking in and out of rooms to find tools, it's extremely odd people could go about relatively silently in this underground base once everyone was aware a murderer was among them. The corridors and rooms really have to really big for that to work, though this complex is supposed to be built by some fringe group. So you do need to accept some things for this book to work.
But when it works, it works! Because they have to choose one of the survivors to operate the machine and pull the rock down, they all believe it's the murderer who should do that (because they have already taken a life; the least they can do is help the others). But as they're cut off from the outside world with limited resources at their disposal, Shoutarou is very fixated on the point of making an air-tight case based on logical reasoning, because there's not really much else they can rely on, being locked up underground. By proving beyond any doubt who the murderer is, they hope to convince the murderer to do the "correct" thing to make amends, while meanwhile, Shoutarou also stresses the fact they are not looking for a scapegoat or trying to pin the crime on the easiest person: they need to know for sure for themselves who the murderer is, or else they'll force an innocent person into locking themselves up in a flooding room and they could potentially cause this person's death if they don't manage to return in time after escaping through the steel door and up the ladder. This does make the first part of the story a bit slow, as there aren't really many usuable clues available yet, and all they can do is wait as the time limit approaches (which does lead to some parts where almost a whole day passes without anything really happening, so it feels a bit hasty at times).
But thing starts to become tenser once you're past the halfway point, with more murders happening and of course the stress slowly building as people start to clash with each other (which is also partially because you also have the family of three who are "outsiders" to the other people), but also long-time feuds starting to flare up. The second murder is especially gruesome, but it is also basically the starting signal for the detectives to really begin their work, as we finally have clues and situations that allow us to make meaningful deductions about the murderer, about how they committed the crime and how their actions will, in a logical manner, eventually lead us to their identity. This culminates in a fantastic denouement scene, just before the deadline as the water keeps on rising. The logical chain used to point out who the murderer is, is quite impressive. While in terms of "events", I'd say there happens less than you'd expect initially and it's not a very long book at any rate either, but there are surprisingly many hints and clues spread throughout the narrative, and some of them are deliciously clever. Objects the murderer used, places they must have visited, all of that is stringed into a surprisingly solid chain of logic, eventually pointing to one and one character alone as the murderer. When it comes to the strenght of the reasoning pointing towards the murderer, I'd say Hakobune is a really strong novel, and definitely a recommended read for those who like Ellery Queen-like mystery novels with long chains of deductions based on the physical evidence and what they say about the actions of the murderer. The way a small hint first leads to a seemingly innocent observation ("Okay, so that clue means the murderer did that. So what?") but then snowballs into something more important until you have a really big indicator of the identity of the murderer is great and I also like how the deduction revolve around certain objects you seem far too seldom in puzzle plot mysteries even though they are so common. The way they are used here is very natural, but cleverly done, and therefore very satisfying. The big climax, after the murderer has been denounced and they are asked to pull the rock down and lock themselves up for the time being so the others can escape and find help is also great, and actually also form a small mystery narrative on their own, as more cleverly hidden clues are used to facilitate this great escape epilogue. The epilogue was certainly the cherry on top of a very cool mystery novel.
But you do have to roll with the initial artificial set-up of Hakobune for it to work. If you can get to that point, you're treated to a very impressive closed circle mystery novel that has a very memorable chain of deduction at the end denouncing the murderer in this unique, almost absurd situation. I can definitely see why it ended up so high on many of the major annual mystery rankings, as it is not only a great mystery novel, but the tense underground closed cricle situation also allows for some cool drama, and it never overstays its welcome. The book definitely has made me curious to Yuuki's other books, so I might explore those in the future.