First, Ayano is not dead. She obtained a snake and came back to life. She just stayed in Kagerou Days intentionally to screw with Saeru no Ebi.
Either way there is going to be total of 10 snakes left, excluding Saeru no Ebi who most likely will die in the good end. In other words, not enough to bring everyone back to life.
I have a feeling that Ayano will eventually give up her snake so Hiyori can came back.
|