Kappa

Kappa are thought to be the spirits of children drowned in rivers, or the offspring of the river god. Some accounts link them to Chinese river demons who crossed the sea.

Roughly humanoid, the size of a child, with green or yellow skin, a tortoise shell on the back, webbed hands and feet, a beak, and a concave dish on the head that must remain filled with water.

Expert swimmer and wrestler. Can drag humans and horses into rivers. Carries a mystical organ called the shirikodama which it extracts through the anus to steal life force. If its head-dish empties, it loses power.