イソラ

Isora is a kappa that lives in the Motoki River, north of Tokieda's residential area. As a child, Keiji spent a lot of time playing with Isora and developed a sort of friendship with the kappa. With ten years having passed since her days of playing in the river with Keiji, Isora is looking to pick up where they left off. To her surprise, Keiji being older means his interests are elsewhere now. 

As the osananajimi character, she has had a thing for Keiji since he was a child, and can be notably jealous when she sees our protagonist around other girls.

Moroboshi Yuumei's review