Wait, I think I was lost at the part when Hisa's reincarnation met Ono. How? I meant, how ...

When Hisa decided to become a human, he was sent back to the moment he died (except this time he didn't die). So presumably he went through the same cycles of reincarnation from there. Ono continues to work in hell after Hisa leaves (he mentions not getting used to Usu's new not-god appearance). What doesn't make sense is how Hisa's current reincarnation had a paper crane folded by Ono lol

I feel like one of the gods or even ran or usu made sure that the crane would show up with the newest reincarnation so ono would know for sure that it was hisa.