No, I don't get the cover.
It's not a normal birthday party however, as Toshiko's future will be decided here. Her father only allowed Toshiko to become an actress on two conditions: she was not to have any affairs with men, and at the right time, her parents would decide whom she would marry. That time has come, and at the party, her father will annonce which of the two suitors of Toshiko (a medical doctor and a laywer) will marry her. To his surprise however, Amachi also learns other guests include a professor involved with the power struggle at the university, and even the student who accused Professor Saijou. The gathering at the Saijou country house is to take place over two days, and nothing has been announced at the end of the first night. The following morning, the Saijou couple is nowhere to be found. At first, everyone thinks they're out walking, but after some hours, everyone becomes worried and start looking. Eventually, the couple is found dead in an old storage cellar located on the grounds. Before the war, the four-meter deep cellar was used to store coal, but it hadn't been used since. The poisoned bottle of water explains how the two died, but not how or why, and there's also the problem of the scribbled letters "WS" on the floor. The door at the end of the stairs leading into the cellar however was locked with a padlock from the inside and the key found in a deep drain inside the cellar, while the only other exit would be the ground-level window four meters up. While Toshiko's devastated by her parents' death, the two suitors haven't given up on Toshiko and the vast fortune she'll inherit. They insist that the person who can clarify why her parents died like that can marry Toshiko, and it just so happens they all have very different theories whether this was some accident, suicide or murder. However, the two suitors perhaps seem to have forgotten all about Amachi, as he has a different theory all together...
This was an interesting locked room mystery, even though the set-up takes a long time and the core premise is a bit wack. For this novel follows a structure with multiple solutions, where both suitors and Amachi eventually propose their own take on the death of the Saijou couple, but let's be honest, nobody's going to believe this is a suicide despite the initial appearance of the crime scene, especially not if we're only halfway into the book and there's plenty of pages left including chapters which are literally titled "Hypothesis of Murder" and "The Truth". But before the reader gets to the more interesting parts, they'll have to wade to a slow start which introduces the backstory of Toshiko, her parents and their relation to Amachi, the other guests and a detailed explanation of the cellar where the dead couple is found. I wonder if this story would've worked better in a shorter format, because some parts feel too undeveloped for a full novel, while other parts feel too long for a short story. Of the thirteen guests present at the party for example, probably only about half of the characters get significant screentime while the others are basically only acting as background filler for most of the story, simply 'being there' in the scene but never saying anything. Add that to the fact that it takes about half of the book before murder is seriously considered an option and you have a novel that is taking things a bit too slow for most readers.
Also: this first half is a bit frustrating because the whole proposal of the two suitors to do the deduction battles is utterly unbelievable. Whether it was a suicide, accident, murder or something else, Toshiko's parents died a tragic death just one day earlier, and they think the way to woo her is to prove it was a suicide/murder/whatever and force her to marry whoever comes up with the best solution that explains her parents' death. Immediately. after it all happened? "And that's why your parents commited suicide. Let's marry!" I'm pretty sure that's going against etiquette!
By the time we arrive at the theories that propose actual murder, and the story develops further as it sets-up the final denouement, Kyuukon no Misshitsu becomes a much more enjoyable story. While the part surrounding the dying message isn't that memorable, the locked room mystery and the build-up towards the solution are quite good. Both the fake murder theory and the final solution are built on clever clues sprinkled throughout the first half of the book, and they don't expect the reader to just come up with the solution for the locked room murder out of nowhere, but challenge the reader to pick up on minor clues and events and combine them to first figure who could have committed the murder in terms of opportunity, and from that point, how that person could've done it (i.e. what the specific options were for that person to set-up the cellar murder). The locked room mystery itself is also quite memorable. The location itself is a bit 'boring' as it's just a cellar locked from the inside and one window several meters high up at ground level, but with the padlock, the key in the drain pipe, the poisoned bottles of water, the message WS, and no signs of ropes or other climbing tools having been used through the window, there are plenty of elements that allow the characters to come up with very different theories, all based on the same information presented early in the story. Ultimately, I can see why Arisugawa decided to include this book in An Illustrated Guide to the Locked Room 1891-1998 as in a few months, I'll have forgotten about the characters and everything of this novel, but even in a few years, I will remember how this locked room mystery was created.
I'm not sure whether I'd really consider a classic of the locked room mystery, but Kyuukon no Misshitsu is definitely worth a read if you're interested in impossible crimes. Considering most mystery novels I read nowadays are relatively recent (most of them actually post 2000), it does read as a dated novel at times in terms of set-up and characters and sometimes this book becomes very melodramatic, but I think the locked room part of the story still holds well. Worth a read if you happen to come across it!