INTRODUCTION
I decided to start writing a review for each of the zaregoto volumes because at a certain point I realized how interesting this series was both as a mystery and as a psychological one and how it was taking me a lot.
Given therefore that this review of all volumes (I hope to be able to do it in a very concise way) was also created to make this series known and appreciated to others, ONLY MINOR SPOILERS will be made that do not go to ruin the story, having said that good reading and I hope you like my review.

Short Summary
the story is about a group of people considered geniuses in their respective fields who are invited to Wet Crow's Feather Island by Akagami Iria, the exiled daughter of a powerful family.
Among the guests is Tomo Kunagisa who has brought with him an unnamed boy who will be called Ii-chan, our protagonist and the only one of the guests who is not a genius.
Our protagonist here, as in the whole story, wants to keep himself out of trouble but on the island there will be a murder, a beheading and it will be up to him to solve the mystery.
General Plot
As a presentation of the main characters, a really good job was done, a very captivating story that takes the reader and gives him all the information to be able to reveal the culprit, also following the reasoning of the protagonist and obviously paying attention to the details that at a first look might seem superfluous, but they prove to be essential.
The topos of the villa isolated from everything and everyone and the topos of the very famous closed-door murder is resumed, but the latter is reconstructed and exploited then adding other murders going to tangle the skein and tease the reader while keeping his interest active.
In general, therefore, a typical narrative of a self-respecting mystery, perhaps with some dialogue that is a bit too long which risks dampening the narrative rhythm; but overall the book is read very quickly until you reach the conclusion that it could leave you confused but instead reserve a pleasant surprise .....
Characters
Ii

Spoiler, click to view
Our protagonist is a very interesting character and perhaps I would say one of the most interesting of the whole series because unlike many of the protagonists he does not have brilliant skills or hidden abilities, his only ability is to be the weakest, and it is precisely this ability that makes him incredible in my opinion because just being the weakest he is able to do things that others would not do.
But his weakness must not only be understood as physical but also mental and character weakness, all this is accentuated by the first-person story that manages very well to get you into his mind and to follow all his reasonings that are very simple and trivial but that despite this they manage to make you feel like a detective because of the great ease of identification that you can have with this character, because it is much easier to feel the weak in the midst of the genes at times rather than the genius among the genes.
Tomo Kunagisa

Spoiler, click to view
Tomo Kunagisa is a very particular character just for his condition, but above all for the very controversial relationship he has with Ii-chan.
Her character has something similar even if distant to Angelman syndrome for some symptoms, for example the fact that she mainly expresses happiness or that she is much younger than the age she shows, this has also led her in my opinion to manifest superior skills in other scientific fields that have made her what she is, a genius.
Personally I find her character very curious but also very shrouded in mystery, precisely because little or nothing is known about her, we do not know why she loves Ii so much or why she cannot climb the stairs, because if we are given slight reasons you feel that there is something in the shadows, something that the author will reserve for the story later on.
Her relationship with Ii-chan is very indefinite because they go from looking like lovers to seeming strangers to looking like brother and sister while maintaining an aura of mystery even if this point, also hinting here some things that happened in the past, when the protagonist says for example that he has felt something intimate with her, forcing her in a way.
What you can guess is that maybe the two were together and then they broke up I think because of the protagonist because she still seems to love him and longs for him while Ii-chan seems to almost hate her to death and love her desperately at the same time.
Aikawa Jun

Spoiler, click to view
And here comes my favorite character of the series, known as Humanity Strongest, she represents in the first volume the classic detective who always knows everything and who manages to make impossible connections to a reader, enhancing an out of the ordinary intelligence.
Her style and character are also strong and unique, they would allow you to recognize her in the midst of a thousand, but the really incredible thing is the contrast that is created between her and the protagonist who are two opposite poles, or the weaker comparing with the strongest; I really appreciated the narrative choice of inserting such a peculiar character only at the end because she helps to keep the interest very high and to create further hype for the following volumes.
Another interesting thing about the confrontation with Ii-chan is that theirs represents the confrontation between the omniscient detective who always manages to connect everything and find the most brilliant plans and the reader who becomes an investigator but who cannot and cannot solve the case. for lack of basic knowledge, really an incredible contrast and a really brilliant thought.
Ibuki Kanami & Akane Sonoyama

Spoiler, click to view
I couldn't help but put together the following characters as I think that they more than Ii-chan and Aikawa Jun can be considered literally two complementary, because of the confusing ending but also for their interactions during the plot.
They represent the two worlds in which knowledge is divided, namely the scientific one (Akane) and the humanistic one (Ibuki) which are obviously in contrast with each other as one believes in mathematics and how to understand the world with it brings progress and she hates the profession of the other that, being that of the painter, according to her, it does not contribute to human development and that it is not useful for progress.
P.S. the dialogue between Akane and Ii-chan was interesting for understanding the relationship with him and Tomo and she was in general a nice character that get along with all, instead of Ibuki that was more lonely.
Ikari Chiga

Spoiler, click to view
I wanted to insert this character over others not only because it will return later but also because in my opinion she represents the way in which the reader from the outside sees the relationship between Ii-chan and Tomo Kunagisa, in fact she a bit like us in the moment where groups are created to move, he begins to question their relationship; and always at that moment she becomes friends with Ii-chan and Tomo Kunagisa, creating a sort of bond with them, despite the fact that she disagrees with the protagonist about his employer and the way in which he is handling the situation in the villa of she.
Other Characters
Other characters not mentioned above are the medium Maki Himena, the artist's assistant Shinya Sakaki, the head waitress Rei Handa, the other 2 twin sisters of Ikari Chiga, the owner of the villa Iria Akagami and finally Yayoi Sachirono the brilliant chief.
Among them only 2 or 3 are interesting while the others serve only to enrich the story of characters and possible suspects, among these there is the artist's assistant who demonstrates a great fidelity that is always maintained until the end by demonstrating some similarity with the relationship between the protagonist and Tomo; and the owner of the island who appears to be responsible for the death of her twin sister due to the D.L.L.R. Syndrome and for this exiled from the family, even if it will eventually prove false. Interesting is the comparison between her and the protagonist regarding the unforgivability of a murder that she sees in stark contrast (and she will not be the only one to think differently of him in the series).
Finally, the last interesting character is the seer Himena only because he despises and teases the protagonist because as a seer he is able to read his mind and see his weaknesses but also the horrible things that the protagonist has done, said this as he will later say the protagonist she is nothing more than a parasite and her presence is just a nuisance.Final Part
I found the final part very interesting and also the most beautiful and fastest part to read, the best parts are Tomo's effort in climbing the stairs for the protagonist demonstrating his great attachment to him, and the final dialogue with Aikawa which is a beautiful comparison between a person with talent and one without.
Both are my favorite parts as they represent a bit of the whole book capturing both the feeling for the first and the logic / philosophy for the second.
Finally, the way in which they built the crime itself I really liked it because it is as if it had been divided into two floors, that is the resolution of Ii-chan which is the easiest and fastest one that leaves out details but still gets to the culprit, and finally that of Aikawa who explains everything makes everything fit together leaving no doubts about it; an ending that you care in a way also because when you read the first resolution at the beginning you say: "Is that all?" while then you read the second you connect all the points and it is precisely there that you see the great genius of the author and makes this work unique in its kind.

To conclude, therefore, I recommend this beautiful novel to all those who love the mystery genre because they will be able to appreciate something certainly original that earned its author the 23rd Mephisto Award at 20 years of age.
I hope you enjoyed reading, and that the readers appreciated my review and if you liked it please do not hesitate to leave an encouraging like