Kappa.
河童(Kappa)
— River Child
Kappa are Japan's best-known river yōkai, child-sized water beings marked by the dish in the crown of the head, feared for drownings and river attacks yet also remembered in many regions as oath-bound helpers who repay mercy with fish, medicine, or labour.
§Appearance
A kappa (河童, かっぱ) is usually described as a child-sized water being with webbed hands and feet, a beaked or pointed mouth, and a shell across its back. Its defining feature is the water-filled dish, or sara (皿), in the crown of the head. As long as the dish remains full, the creature keeps its unusual strength. If the water spills, it weakens and may even die.
Edo-period books such as Wakan sansai zue (1712) preserve less settled forms as well, including hairy and ape-like river creatures. Over time, artists such as Hokusai, Kuniyoshi, and Yoshitoshi helped fix the more familiar turtle-like and frog-like image. That later form is the one most often seen in festivals, river warnings, and yōkai art today.
§Interactions
Kappa are notorious for challenging humans to sumō, snatching at horses near riverbanks, and dragging the unwary into deep water. In harsher folklore they seize the shirikodama (尻子玉), a mythical organ believed to lie within the body. Because of these attacks, the kappa becomes a powerful warning figure in stories told to children and in cautionary lore around rivers and ponds.
The same tradition also preserves more reciprocal encounters. A kappa is often said to be obsessively polite, so a person who bows may cause it to bow back and spill the water from its sara. Once subdued, it may swear a written oath not to harm the village, bring gifts of fish, help with irrigation, or teach bone-setting and medicine. This double character, dangerous water predator and troublesome neighbor, is one reason the kappa remains central in Japanese folklore.