My version of this book had the first cover, but I had to post that second cover too because it's just too... memorable.
Tsumura Shuusuke was a writer who for twenty years long, worked on The Black Report, a long-running series which fictionalizes real-life incidents. In 1982, he became a novelist with the recommendation of Ayukawa Tetsuya, and two years later, he wrote his first novel starring the freelance investigative journalist Uragami Shinsuke. I had never read any of his works, but he was fairly prolific, writing about four novels each year until he passed away in 2000 and his work has actually been adapted for television too. I myself first heard about this book via Ooyama Seiichirou's Twitter account, who was quite positive about the work. Based on the style of his book titles and Noto no Misshitsu, it's clear he writes in the travel mystery modus: mysteries set in touristic destinations, and often featuring alibi tricks using trains and other modes of transport.
By the way, I do always have a fondness for diagrams in mystery novels that are clearly hand-drawn. Like sure, diagrams drawn on the computer look slick and are often very clear, but there's a charm hand-drawn floorplans have...
Plot-wise, Noto no Misshitsu is pretty much nothing more or less than you'd expect of a mystery novel featuring a train-based alibi trick, and in that sense, it's hardly a surprising book, but I do have to admit I really liked how the book provides a reason why the detective (Uragami) would start to have doubts about what is on the surface a perfect alibi. Early in the book, it is established that if this was a murder, there are three suspects. Masae's father recently passed away and most of his fortune will go to her. The first suspect is Masae's husband, who is cheating on her and owed his father-in-law money, so now his own wife who might be leaving him, the second is Masae's half-brother, who had swindled a company before and supposedly lives a better life now, but still with money borrowed from his father, and Masae's uncle, who also borrowed money. All three of them seem to have pretty solid alibis, so why would the police, without any real cause, suspect their alibis are fake? I remember how in the film edition of Ten to Sen, the way the police detective suddenly decides to suspect someone who just showed he had a perfect alibi was absolutely hilarious because how forced it was (+ the acting was very stilted), but in Noto no Misshitsu, there's a pretty good justification: Uragami is looking for a scoop, so yeah, he hopes Masae was killed in a locked room and the murderer came up with some brilliant alibi trick, because that's what will sell: he has no guarantees it's actually true, but it does give him a reason to try and dig deeper into everyone's stories than the police would. It's a bit silly of course, but it strangely works.
It doesn't take long for Uragami and Miho to start having doubts about the suspect who claimed he was on board the Twilight Express, travelling from Osaka all the way to Sapporo. I usually try to avoid spoiling too much about a book, but the book literally opens with a time schedule for the Twilight Express and a map of Japan showing which stations it stops at, so at this point, even the book itself doesn't pretend like the other two suspects are viable suspects: yes, we are going to focus on that one suspect who was in the Twilight Express. The man was seen during four different times throughout the trip starting late afternoon until the following morning, from when he got on the train, to during dinner and at arrival, so that seems to prove he was there all the time. Meanwhile, Masae was killed in the early evening in Wakura, and while the Twilight Express does go in the general direction of Wakura, it does not pass the town, making it impossible for that suspect on the Twilight Express to kill her. And then there's of course the locked room, which makes it not only impossible for that particular suspect, but for anyone in general.The locked room mystery by the way, is not something to really write home about: while the precise set-up of how it was done is interesting in terms of Tsumura actually clewed it, the trick itself is rather trite, and one of those ideas you could imagine someone who'd never even heard of a locked room mystery to come up with. So while the "locked room" is part of the book's title, don't expect much of it.
As a story focusing on someone with a perfect alibi by being inside a gigantic moving steel box however, Noto no Misshitsu is far more interesting. Mind you, the fundamental idea behind how the murderer managed to create this perfect alibi, while at the same time also committing a murder elsewhere, might not be very surprising: once you know this is an alibi story revolving around a train, it's likely you'll have some idea how it was done. But what Tsumura does do extremely well is... covering his tracks. Like, the basic trick is, on paper at least, very simple, but Tsumura then makes sure the trick actually works by adding little tricks on top of that to hide the main alibi trick, and while it wouldn't be special if it had been only one thing, Tsumura does this so extensively, it actually helps make the main alibi trick really feel like an impenetrable wall. Uragami starts attacking the alibi pretty early on in the book, but each time what appears to be a weak point in the plan, turns out to be covered with a line of defense by the murderer, and it slowly, but surely makes you believe perhaps he's really innocent. While I'm not a huge fan of the main, connecting element that allowed the murderer to create so many walls of defense (it demands a lot of moving parts for this plot work!), I do like how thorough Tsumura was with plotting this perfect alibi: you really can't be sure it's over until it's over, for each time the murderer conjures up a new bunny from his hat. In this regard, you can see how Tsumura had been writing these novels for about a decade by then, so it's a very competently constructed puzzle.
I wouldn't call Noto no Misshitsu - Kanazawa Hatsu 15ji 45pun no Shisha a particularly remarkable example of a mystery novel with an alibi trick, but it is competently plotted and a pretty solid read on its own. It's definitely written by someone who has a lot experience penning such novels relying on train time tables, and I do enjoy reading them once in a while, so I might read more by Tsumura in the future too.