Putting aside a critical matter for a moment, to some extent it's both more fitting and better revenge (mixed with redemption) if Aqua gets through to Kamiki that this wasn't fiction and that his whole basis for things was wrong. If he makes him truly and deeply regret it even while he's punished for it, vs "ah well someone better caught up with me", by undermining the foundation he lays out here. But the critical matter can't be put aside long:
How is this dude going to justify driving the incel to commit suicide and killing Katayose Yoru
Also Goro, aka, Aqua himself.
That we know of. And yeah how Aka resolves that is going to be central IMO to whether he can stick the landing here, and I wonder if he wrote himself into something of a corner. Having the fan who killed Ai kill himself actually would kinda fit in a twisted manner, he was "just a tool" and "even if instigated, he's still guilty".
But killing completely unconnected people including a medical doctor, and continuing to murder and reveling in it for a decade+ afterwards? That doesn't really work. Maybe even Goro can be explained by the whole period being a black one of insanity he regretted afterwards, but that definitely doesn't apply any time afterwards. Kamiki's character in all the plot so far would have worked just as well if he had never hurt anyone else ever again afterwards. He'd still be guilty as hell, he'd still be covering it up, others would be too. Killing that actress had zilch to do with the core plot, it was just a "look how bad this guy is!" set of pages. Having established this guy has been a serial killer ever since, I don't think that's redeemable particularly given he doesn't seem to be bringing that up and there is no sign Aqua or anyone realizes it (and really, how could they?).
In some types of stories the Unreliable Narrator mechanism could play in, where it turns out this flashback isn't actually 3rd person omniscient but what Kamiki is revealing to Aqua, and in turn Kamiki is either lying or conveniently distorting thinks. So the readers themselves are challenged to interrogate what they're seeing and being told and not necessarily believe it. OnK hasn't really run that way though, flashbacks have been time travel flashbacks, seeing history play out. Maybe if challenged right away next chapter. But he'll need to face real justice. Anyway, guess we'll see.
I'm a little disappointed so far that so much has been focused purely on Kamiki too. Maybe more is planned for later, but still I thought there'd be a little more dealing with the large entertainment world and nature of power. In earlier sections it seemed like there might be more interrogation of who stood to make money off of looking the other way of a variety of dirty business culminating in the murders. So far though it's become very singular, more so then I expected.
I guess just in general it feels like a bunch of threads that were built up over the course of the series just got dropped hard in the last few chapters and it all rushed along. Granted that happens with plenty of manga but still too bad.