Can anyone with better reading comprehension and attention span explain to me what just happened to the main character? Is it him? Is it not him? Are his personalities merged? What is going on? Hilfe!
Disclaimer: I've only read this as far as this, so errors might exist, while uncertainty for sure does.
Essentially, the main character (Ao) in certain ways is exactly as he was at the start, the big stuff in some ways happened in the past. So, some unknown time ago, he drank(?) poison meant to/capable of killing these aberrations for good. That poison, as it turns out, was at least in some part made out of the heart and liver of another boy. Ao did this knowingly, but for unknown reasons related to remorse. The "other" one we saw when what seemed like Ao woke up and got jumped by Miyako is probably the owner of that heart(ch26p4), that Ao apparently "killed" either by said consumption or something related to it. Why the
other one woke up now is unknown, but we have a massive clue in the preceding chapters, where Hachishaku-sama/Yae bit off and swallowed his finger a few days ago, which apparently caused Ao to somehow grow gradually "weaker" in his feverish state.
Now, as an aside I'll have to say that I don't agree at all with people here jumping to the conclusion that this story makes no sense in the least or that there is nothing laid out. There is, but much of it is shown and alluded to, instead of directly exposited and some of it requires some context, like the whole mystical concept of
Gu(/kodoku) that is constantly played around with.
People probably just didn't read it through the whole thing with thought and spent attention on context, but instead of read through quickly one chapter at a time when it released. This thing is full of mysteries, half-explanations and allusions, so this release schedule probably really ends up hurting the story quite a bit. And yeah, it's still a Mystery story with capital M.
To everyone reading this: If you have the mind to it, I recommend reading up to this point while paying attention to what is said and the and the imagery. Stuff like ch15p23, ch17p13, ch25p17, ch26p6. Seriously, there's a ton.