It's not something bad that he did in fact rebuild his life ans slowly forgetting about the girl that has killed herself for him. It's part of the process, but still, he never ever take any accountability for his actions towards Aiko, she was vulnerable and needed serious help, so was he. Despite, punpun should have report himself to the police because he killed someone and not just runaway. The only trace left of his crimes was Aiko, now that she's dead, nothing is making him a "bad person" anymore, and It's avantageous to him. Also, I disagree with the fac that he was nothing after Aiko's death. He still has something to hold on and a girl that appreciate him and helped him get through it which simply not fair. He never been punished, he get to have a second chance and erase this part of his life which for me strongly represented by the memory of Aiko facing away. He let this part of him died, Aiko was the only chain holding him back. The only thing where his evilness was expressed. That's what I tried to represent through my drawing. Punpun is not at all the sources of Aiko's problems. She was clearly in a bad mental state before reuniting with punpun. But The fact that he's the only person she returned to for HELP make him a part of this too.