This is a very well crafted and structurally satisfying book, and the mystery explores many layers of logic and ultimately has a very satisfying conclusion, both in the Queenian sense of being very attentive to the small clues and the intricate logic as well as in the sense of being surprising and impactful.
It is also the most cursed book I've ever read. I don't know how you can write this without holding an utter disdain for the human species. Its first half made me feel physically ill at times, and ending made me spiritually ill, and the fact that a book can get that kind of reaction out of me, a Maijo fan with a hardened stomach, is something I do respect. I don't think I'm coming back to Shirai for a few months though because I can't handle two of this kind of story in a row.
I am also slightly disappointed in regards to the usage of the special setting. While I think the mystery uses it to great effect mechanically, there are many areas of thematic exploration they could have gone for that Shirai seemingly didn't really care about, such as . I think he could have explored some of these ideas in the off time the book has, because while I would not say it drags at any point, there is definitely a lot of time spent doing not much other than building the mystery, and most of the characters I find pretty bland.
Still, while I can't imagine a story more opposed to my personal sensibilities, that's part of what makes it fun to explore. I could have never written a book like this, and those are often the books that stick out in my mind the most, especially when they are as well constructed as this one.