I think the overall plot line and twists work, but there ends up being some disconnect between the themes, so the story doesn’t work on that deeper level.
Kazami’s murders and the copycat murders consistently involve themes of identity, freedom, and outside structures.
Doll murder = she makes some obvious comments about societal control and why she picked a high school girl for her original murder.
Clothing murder = “the clothes choose you”
Chair murder = “chairs fix people in place”
Body parts made into one person, random choice used to decide things instead of your own intellect.
You have to assume it’s all supposed to connect to the fact that the two main characters aren’t who they say they are, but then it just…doesn’t? Kazami seems entirely confident that she’s Kazami (despite playing someone else for a year), and that Koto is Koto. We’re constantly given these philosophical arguments about Identity, but then the manga seems to throw all of that out so the scenes at the end can be sappy and meaningful. Kazami doesn’t seem to believe in her own thesis (or I guess maybe since she’s murdered 89 people she’s figured out her questions about identity properly and feels really secure in the existence of a true self).
There’s just no point in belaboring the idea of identity if the characters exist in a world where they can just hop back into being their true selves. It means that there wasn’t anything to be worried about (unless you’re specifically a guy who’s secretly a hypnotized serial killer girl, but that’s not true for most people).
Also Koto should have gone to jail. Sorry Koto
Asagao is the real person who got distorted over the course of the story. Did the beauty of girl’s love make him forget about “accessory to murder” being a crime
P.S. I think “Asagao Nemuro” is a reference to the manga “Mori no Asagao”, a manga about death row inmates which earned acclaim. It also happens to be on mangadex!