The water-dwelling yōkai said to have a dish-like depression on its head is the kappa.
Kappa are usually described as small, humanoid creatures that inhabit rivers, ponds, and other bodies of water. Their most distinctive feature is the sara, a plate or dish on the top of the head. Folklore says that the kappa’s strength depends on the water held in this dish; spilling it can weaken the creature.
Stories portray kappa as dangerous, mischievous, or occasionally helpful. They are traditionally associated with swimming hazards and are said to challenge people to contests. Some tales also emphasize their fondness for cucumbers, which are offered as gifts in popular retellings.
Kappa belong to Japanese folklore rather than being kami in the strict Shinto sense. Their legends vary by region and historical source, and modern manga, games, and films have given them many friendly appearances. The head plate remains their most recognizable identifying feature.