And finally I make an account, just to comment on this thread. This manga is something of a masterpiece, and I never would have guessed I'd like something with such fucked-up subject matter this much. In terms of both writing and art, it's way beyond most of what's out there. (What's the comics/manga equivalent of cinematography? Taiyaki's a master at it, whatever you call it. The angles and perspectives and the way emotion is visually conveyed in this manga are all incredible.)
In response to Liliwyrt's theory — I think that may be in the general area of what's going on, but I don't think that's quite it. If that's what it was, it would basically just mean that Ayako was carrying around a bunch of internalized homophobia, and I feel that mixing up the issues of Ayako struggling with being a lesbian with the incestuous side of things could very easily end up having a bunch of unfortunate implications. Given that Taiyaki is a lesbian herself, I don't think she would go there. I think there probably is something going on with Akira and whatever happened to Atsushi, but we still don't know what. I have some ideas about what's happening now and where this is going, but it turned into pretty much a whole essay when I went to write it out. I'll share my thoughts once I've trimmed it down a bit...