A Kappa is a Japanese Under Fae.
Wayne found a starving Kappa in a well in a cave in 1942. He chained the Kappa and supplied it with girls for food, taking advantage of rejuvenating properties of the water in which the Kappa lived.
Kappa appear to have heightened strength and to some extent speed. However, their most important quality appears to be their resistance to harm and healing abilities. They seem to feed on females, using the nourishment they obtain from them to trigger the healing process, which can be imparted upon the waters in which they immerse themselves in. Humans who drink from this water receive similar benefits, like longetivity and vitality. When Bo fought a Kappa, she appeared unable to seriously damage it. The easiest way to kill a Kappa is to knock the top of its head off, spilling fluid out of its head and immediately killing it. Dyson notes that they have a "Tea Pot" head.
Kappa are a yōkai found in Japanese folklore, and also a cryptid. A hair-covered variation of a kappa is called a Hyōsube. There are more than eighty other names associated with the kappa in different regions. Along with the oni and the tengu, they are one of the most well-known yōkai in Japan.
- 1.03 Oh Kappa, My Kappa