He went out and hanged himself and then there were none.
I finished the Watanagashi chapter of Higurashi: When They Cry, so I added my speculations/questions about that episode to the memo page for my playthrough of Higurashi: When They Cry.
Back when I first started reading Japanese mystery fiction in translation, there wasn't that much available. One of the authors I "missed" back then was Natsuki Shizuko: while a handful of her work had been translated to English, the books were all out of print by the time I started looking, and you didn't really see them pop up often in the used market. And eventually, the one time I did end up reading Natsuki in translation, it was a rather funny experience, as I found the German translation of an English translation of one of her works in the club room at my Japanese university. Anyway, I never did manage to read much of Natsuki despite her (theoretical) availability in English, but I do remember slogans and blurbs describing her as the "Japanese Agatha Christie": a translated book can probably only sell if you push the author as the [Nationality] [Super Famous Novelist]. Interestingly, the book I had read, Mord am Fujiyama, was originally called W no Higeki ("The Tragedy of W"), which would suggest Ellery Queen more, but in terms of actual story, it did feel more Christie-esque.
Soshite Dareka Inakunatta ("And Then One Was Gone" 1988) is another novel by Natsuki with a title based on a famous work, in this case of course being And Then There Were None by Agatha Christie. Unlike Mord am Fujiyama however, this story is written explicitly as a homage to Christie's famous closed circle mystery novel, staying very closely to the plot structure of that work. The book opens with the arrival of several people at a harbor. Haruka, the daughter of a hotel owner, has been invited by Mr. Uno for a week on his cruiser with a few other guests, which will bring them all the way to Okinawa. The Uno clan is a major force in the Japanese society, with patriarch Uno at the top and his (illegitimate) children heading several leading companies, so knowing this is a chance of a life time to make connections that will help her for the rest of her lief, Haruka of course agreed to come along. She is joined by four other guests, a lawyer, a doctor, a professional golfer and a writer on the cruiser the Indiana, which is manned by two crew men. The five guests are informed that Mr Uno is delayed, and that he'll join them the following day, when they'll pick him up at the next harbor stop. The first night, Haruka and the others notice that there are porcelain figurines of the Chinese animal zodiac in the living room, but oddly enough, only seven animals are represented. When they also spot a copy of And Then There Were None on the shelf, Haruka is overcome by a funny feeling, realizing that the cruiser Indiana, and their host Mr. Uno reminds her of the book's setting Indian Island and the host U.N. Owen. But just like the book, a tape starts playing during dinner, in which each of the seven people present on the cruiser are accused of having murdered someone, or directly caused someone's death. They all hope it's a very bad joke, but the following morning, one of them is found dead in his cabin, apparently having committed suicide. The captain informs the authorities and they hurry to the nearest harbor, but the engine, the navigation systems and the compass have been messed with, and soon they find themselves drifting completely off-course, and then another death occurs and it's clear this one is actual murder. Can the remaining five survive this floating closed circle situation?
Describing Soshite Dareka Inakunatta as a homage to And Then There Were None is honestly the only way to describe it accurately, because I don't think this novel works without the context of And Then There Were None. While the characters aren't killed one by one based on a nursery rhyme, names like Mr. Uno and the Indiana, and the accussations of murder to each of the persons present on the cruiser and all of that show this book is styled very closely after Christie's famous work. In fact, the characters themselves notice this and they even spoil part of the solution of And Then There Were None without any warning, so yes, Natsuki really expects you to be aware of the plot of And Then There Were None. Which is basically the reason why the novel fell a bit flat for me, for while Soshite Dareka Inakunatta is decent enough knowing it is a homage, it isn't as amusing when reading this novel as a standalone story. So much feels too familiar, and the cramped closed circle situation (the cruister) feels a bit too small for this plot too really work. Having either an unknown third party or someone within the group be the murderer who preys on their victims while on a fairly large island is one thing. With a group of just seven (let's say six, for they only know they are might be in danger once the first one dies) all stuck on a private cruiser, it just seems a bit hard to swallow anyone could commit multiple murders without anyone noticing if the others would actually try to prevent them. Knowing this is a And Then There Were None homage, I could kinda wave this away, as I knew this story would have to unfold in a certain way, but otherwise, you're just left wondering how a murderer could ever succeed in committing these murders one after another without anyone noticing.
An important difference in narration between the two works however is that this book is told solely through the eyes of Haruka (except for the epilogue), which does add to the sense of suspense. In And Then There Were None, the player follows all the characters at one point or another, which helps sell the mystery of the reader wondering whether the murderer is among the people on the island or not, while in Soshite Dareka Inakunatta, the focus is more set on the thriller-mode, with Haruka being pretty helpless on the cruiser, with people dying around her, the cruiser being off-course, and Haruka not being able to do anything about this. It results in a book that's easy to read on an afternoon, but with the smaller cast and the focus on Haruka, it does mean everything feels rather light, as plot developments follow each other fast while there's not really much any of the characters do while on the cruiser while they're being killed one after another.
That is part of the reason why as a mystery novel, Soshite Dareka Inakunatta does feel a bit underwhelming. It reads more like a thriller most of the time, and when everything is done and we get an And Then There Were None-esque epilogue where everything is explained, you're presented with a solution that is obviously written as a direct homage to the solution of Soshite Dareka Inakunatta, but it's not rewarding at all on its own. You're basically told that the culprit chose the most convoluted and least certain method to accomplish their goals, which of course makes no sense at all if you just read this book "as is." As an And Then There Were None homage, there's room to make interesting comparisons between the solutions and the plot structure of both works, but that's basically it: the whole plot of Soshite Dareka Inakunatta only works as a direct answer to And Then There Were None, with some scenes mirrored on purpose on the original work, but a lot of the novel doesn't work "in-universe", only for the reader, and specifically a reader who knows And Then There Were None. And while one can definitely argue about how "fair" And Then There Were None was, Soshite Dareka Inakunatta definitely has even less clear clewing for the reader, so at the end of the day, it's a mystery novel I wouldn't recommend as a standalone read.
If you're looking for a work specifically inspired by And Then There Were None though, I guess Soshite Dareka Inakunatta can be entertaining. The story's not just based on the same premise, but definitely written on purpose as a way to interact at several levels with And Then There Were None in an almost fanfic-esque manner, This is definitely light reading, but as long as you're aware of that and go in knowing it's staying very close to And Then There Were None by design, it can be a familiar-feeling, but entertaining read.