No, this book is not set in a place where rocks levitate...
It has been three years since the traumatic events at Katsuragi Teruyoshi's family home, and now the great detective and his best friends Tadokoro Shinya and Mitani Rokurou are all studying at different universities, all having an idea of their future. They still see each other often, but they have not travelled together in ages, however, exceptions are made for special occassions: Katsuragi and Tadokoro have received a letter from Asukai Hikaru, the former high school student detective whom Tadokoro looked up to when he was young. A few years ago, Katsuragi and Tadokoro met her, now in her late twenties and working as an insurance agent, at the house of mystery author Takarada Yuuzan, where they were confronted with a horrible murder. Katsuragi and Hikaru had clashed about their views about what a detective is, so Katsuragi and Tadakoro are surprised to learn she had written them a letter. She informs them she's going to be married to Dotou Kouki, the son of Dotou Raizou, the world famous multi-disciplinary artist, especially known for his paintings, sculptures and architecture. While Kouki is "a normal guy", his sisters have inherited their father's artistic talent, with Yukie being an accomplished illustrator, Tsukiyo a sculpter and Kanon a singer. Because of Kouki and Hikaru's engagement, they're going to have a rare gathering on the last day of the year at Raizou's home the Wasteland Manor: a house with four towers Raizou himself designed, located in what is basically a small, square valley, with the house surrounded completely by four rock walls.
Raizou turns out to be a friend of Takarada Yuuzan, who has passed away since. It was Raizou who designed the house of Yuuzan, and in exchange, Yuuzan had written a mystery novel set in Raizou's home. It is this unpublished manuscript that worries Hikaru, prompting her to contact Katsuragi and Tadokoro. It appears Hikaru's presence at Yuuzan's manor three years ago had not been a coincidence, but set-up by Yuuzan, and she fears she's being manipulated again by this unpublished manuscript of Yuuzan. She hopes Katsuragi and Tadokoro will come to the house, as her "relatives" and see if they can get their hands on the manuscript and see what is hidden within the pages. Katsuragi has no intention of meeting Asukai again, but he agrees to at least join Tadokoro and Mitani on their way to the house. The three young men meet with Hikaru and Kouki outside the house to discuss what they'll do, but then they are surprised by a heavy earthquake. While they are all unharmed, the road has collapsed and trees have fallen on the road, blocking it completely. Very conveniently, Katsuragi alone finds himself on the outside world side of the road, while the rest are now trapped on the house-side of the road. Katsuragi says he'll go to the nearby town and stay there, while Tadokoro and Mitani will go with Hikaru and Kouki as planned.
This is the third book in the series which now bears the name Manor Quartet, which obviously suggest this series will be four parts in total. The first book had fire and the summer as its theme, the second water and autumn and this third book revolves around earth and winter. So yes, that suggest the final book's theme will be wind (air) in the spring. A murder in a house during a typhoon? Anyway, I enjoyed the previous two books about Katsuragi, the young detective who has the ability to sense people lying to him, and while I had not read the premise of the book before, I was pleasantly surprised to learn that Asukai Hikaru from the first book returned too in a prominent role, so once I got started with this book, I had gone through it really fast.
The book takes on a rather interesting structure: the first third of the book is actually an inverted mystery: we follow Ogasawara Tsuneharu as he makes his way to the Wasteland Manor to kill Raizou, whom he hates for a very personal reason, only to find the road collapsed and blocked by fallen trees. When he grumbles out loud he now can't kill Raizou now, a woman calls out to him from the other side of the road. While they can't see each other, she offers to kill Raizou instead of him, if he then kills the propriator of the local inn. The woman suggest she'll kill Raizou first and use a flare signal so Ogasawara will know she has succeeded in her task, after which he'll kill the proprietor. Ogasawara accepts the offer for a murder exchange, and arrives at the inn, but can only stay he shares a room with Katsuragi. And so Ogasawara slowly starts to plan his murder (luckily, he was already planning to kill Raizou so he has things like poison with him). But as this is an inverted detective, we of course see how Katsuragi slowly starts to suspect his roommate isn't just some innocent guest. But how did he figure it out? This part is fairly short, but I do like the clewing Atsukawa employed to allow Katsuragi to get on the trail of Ogasawara. We know Katsuragi starts to have his suspicions very early on, but the clues that allowed him to zero on his roommate are fairly clever hidden. In the aftermath, Katsuragi learns about the murder exchange, finally realizing his friends Tadokoro and Mitani may be in danger, as there's a murderer in Wasteland House.
At this point, the book jumps back to the last day of the year, and we now follow Tadokoro, who together with Mitani visit the Wasteland House. Kouki's sisters Yukie, Tsukiyo and Kanon seem not interested in the two men, nor are the two other guests (an art broker and Kanon's manager), but Raizou himself seems interested in Tadokoro, as Raizou is aware Tadokoro and Katsuragi where involved in the incident in the house of his friend Yuuzan, and Raizou also seems more interested in Hikaru's past as a high school student detective, rather than as his future daughter-in-law. The following day however, the man is found dangling from the sword of the knight statue in the courtyard, but how could anyone have lifted the victim and stabbed him on a five-metre high sculpture? As there's no landline phone and for some reasons, their mobiles don't have any reception, all they can do is wait until the road's been restored or outside help comes via some other way, but they don't have much time, as more mysterious happenings occur, from sightings of a masked butler who can escape from a tower room with only entrance even though they were being chased by Tadokoro and someone being shot inside another tower room, even though it was locked from inside and the only window in the room looks out... on a rock wall. With Katsuragi not present, and Asukai Hikaru having sworn off ever playing detective ever again, Watson Tadokoro finds himself forced to be the Holmes himself this time...
In Gurenkan no Satsujin and Aomikan no Satsujin, the respective themes of a mountain fire, and a flooded river added a note of excitement to the mystery: like Ellery in The Siamese Twin Mystery, it wasn't just that Katsuragi and Tadokoro found them having to deal with a musterious murder committed in a house, they also had to deal with an unstoppable force of nature, a force that also had its influence on the murders. In Koudokan no Satsujin, we have one major earthquake at the very start of the book, followed by unpredictable aftershocks, but I have to admit I found the theme not as strong here as in the previous books. The initial earthquake creates the closed circle setting, and also sets up the murder exchange, but from that point on, we just have aftershocks happening now and then. They don't really serve as a constant threat, as they come and go swiftly, and it's not like you can predict them. The earthquakes are not a theme that permeate throughout the novel, only popping up now and then, so that kinda weakens the "earth" theme, even if the couple of themes they do feature in the mysteries, they are integrated cleverly.
That said, I do find the whodunnit rather disappointing. The first part is an inverted mystery, so of course who the culprit is, but Ogasawara himself never learns who his partner in crime is, so we don't know who the murderer inside the house is. However, the way Atsukawa planted the clues to point to the murderer are a bit too obvious. While from an in-universe point of view, it makes sense it takes some time for the detectives on both sides to catch up as you need information obtained from both in and outside the house to solve everything, it doesn't mean the reader isn't already in possession of that knowledge, and it makes the attempts to present false solutions feel a bit weak, as you know the big elephant in the room hasn't been addressed yet.
Overall though, I do like how this book is set three years after the previous books, with a more mature Katsuragi Teruyoshi who has learned to deal with his trauma gained in the previous two books, and we see how that also helps Asukai Hikaru, who has her own trauma. I'm not really that interested in character development, but for those looking for that in a detective character, you can definitely find it in this series, and what I do like is how Katsuragi's character does influence his detecting style a lot: it's his experiences that leads him to act like he does now as a detective, so in that sense, I do like seeing the change in him, as it's directly reflected in the way the mystery is plotted and how Atsukawa decides to have the story solved.
Koudokan no Satsujin is overall a solid third entry. While the earth theme isn't as strongly present here as the force of nature themes in the previous two books and it is overall a bit simpler, I do like the twists Atsukawa presents here, like having an inverted mystery section, and focusing on basically three detective figures in Katsuragi, Hikaru and Tadokoro. Can't wait to see how the last volume will wrap things up!
