For people who are confused about why it's coming back to Kamiki, after a couple chapters ago Aka cast him as somebody who killed Ai because she dumped him but actually she loved him the whole time, with Nino supposedly being the person who was the "mastermind"...
Remember that we readers saw Kamiki kill an actress a while back, pushing her off a cliff casually. So he is some kind of experienced serial killer whose issues go way beyond a fixation with Ai. And apparently Aqua has picked up on that, which is why he shows up at the end of this chapter. Finally, Aka is giving us a confrontation with the real Kamiki, something I've been waiting a long time for.