they probably meant that they're confused whether ai was kamiki's first crime. for example in the recent chapter, it's shown that kamiki doesn't seem to be the murder of taiki's parents. also there's the doctor, it might be done by the stalker without kamiki's help. after this chapter i felt that kamiki was a bit more normal and sane, it doesn't seem he would go as far killing an innocent person like the doctor. i might be wrong tho. after all previously he also killed that female artist... uhm for reason that i forgot. anyway all this time we all thought he's very murderous towards female. now it seems a bit funny. it seems his previous interaction with ruby was just him tried to be a father for once, bleh.
i will take further guess. all this time it seemed no one expected kamiki to get jailed, social's death seems to be the expected scenario. maybe because he 'only' provided information to the stalker (and there shouldn't be hard evidence left behind), he could shifted the blame and said that he didn't know the stalker would do that to ai. japanese law probably couldn't caught him for it at least
I don't know if that flashback is from the 15 year lie movie or from Hikaru's POV, but at least we get to know the entire story (๑•ㅂ•)و✧! I already felt that the backstory from the previous chapters is still not enough. With this and the continuation on the next chapter, we will finally get to know the other part of the plot then we'll pinpoint them and arrange them properly in a way that we can understand. I mean, well......am I the only one who still don't understand or feels like the backstory from the previous chapters are lacking? Haha....sorry. Anyways, I wonder why Ai said that to Hikaru. And I wonder who's the first person he killed? If it's Ai, that doesn't mean she's his first victim that he killed with his own hands since it was someone else who killed Ai and even committed suicide after the murder. But if we set aside the "killing someone with his own hands", then Ai is his first victim. But there's also possible chance that Ai is not his first victim. I say that after Ai said that to Hikaru, Hikaru got more worst after being fucked up by Taiki's mother.
Hikaru dude should've went to a therapist before it's too late ╮( ̄▽ ̄)╭. But we still don't know the story from his POV. That wasn't enough for me, I want more from his POV!!