Toilet-bound Hanako-kun manga volume 4 features story and art by AidaIro.

Nene steps into the spotlight! The mermaid kingdom hasn't forgotten her, and they're back to claim what's theirs! Can Hanako protect her from becoming permanently fishy? Meanwhile, Kou makes friends with an odd ghost haunting the entrance to the middle school division. Kou has no idea who this guy was when he was alive, but that doesn't mean he can't help him solve his unfinished business! Will the junior exorcist be able to help this friendly ghost pass on...?