i looked up some reviews and realised that there's an edition of this book with an introduction to the honkaku genre written by shimada soji (also translated by ho-ling wong, i believe), which i think provides some very interesting context for anyone else who's as unfamiliar with japanese literature/the honkaku genre as me!

In the manner of Van Dine, Ayatsuji also did away with focusing on the latest science in The Decagon House Murders, and set the murder and the solving of the case with an isolated house as its stage from start to finish. But he ruthlessly eliminated all the elements which Van Dine had thought necessary to make his stories “literary,” such as the depiction of the American upper class; the witticisms; the attention to prideful women; the cheerful conversations while the wine is poured at dinner; the polite demeanour of the butler and servants. Thus his novel approached the form of a game more so than anything previously written.

As a result, his characters act almost like robots, their thoughts depicted only minimally through repetitive phrases. The narration shows no interest in sophisticated writing or a sense of art and is focused solely on telling the story. To readers who were used to American and British detective fiction, The Decagon House Murders was a shock. It was as if they were looking at the raw building plans of a novel.

People devoid of any human emotion, only moving according to electrical signals: a setting reminiscent of the inside of a videogame. Ayatsuji Yukito’s unique method of depicting such abstract murder theatre plays, in which he hides his murderers, follows the traditions of the “whodunit” game of the Kyoto University Mystery Club. The participants in this game are given nothing in print, but have to guess who the murderer is based on an oral reading of a detective story. In a tense situation like that, where every word disappears the moment it is spoken, there is no need for beautiful or witty writing.

Ayatsuji Yukito first introduced this technique, dubbed “Symbolic Characterisation,” and his experiment The Decagon House Murders was also his debut novel. Some have mistakenly taken his calculated abstractness as inexperience in expressive power or even a lack of writing skill, and he was criticised harshly when the book was first released. However, he had his reasons for writing the book the way he did. And to everyone’s surprise, bot-like characters from videogames became widely popular soon after the book’s release, just as Ayatsuji’s style of detective fiction had already foretold. Thus Decagon found its place among other masterpieces. Anime (Japanese animation) which would soon take over the world, would also feature the closed-off worlds of the Ayatsuji school.