The village chief of the area around the Arakawa riverbend. He is a green kappa that lives in the pond nearby. Only he has the authority to approve every newcomer to the river bend area. Often feels sad because he is discriminated by humans because of his outer appearance.
He is in fact no real kappa, but just an ordinary human that wears a kappa suit, as seen by the zipper on his back, also he might be "that man" who is sectertly protecting Nina's true identity and is her guardian (in anime they have same voice actor).