In Japanese folklore, a kappa is an amphibious yōkai commonly depicted with a water-filled dish on its head.
Kappa are legendary creatures associated with rivers, ponds, and other freshwater environments. Artistic depictions often show them as small, humanlike beings with turtle-like features, webbed hands or feet, and a depression on the top of the head called a sara. The kappa’s strength is traditionally said to depend on the water held in this dish.
Folklore gives kappa both dangerous and humorous traits. They may threaten swimmers or challenge people to contests, but stories also portray them as fond of cucumbers and bound by formal politeness. If a person bows, a kappa may bow back and spill the water from its head.
Kappa stories vary by region and changed over time. They are not identical to every Japanese water spirit, and modern manga, games, and mascots often present them in friendlier forms than older cautionary tales.