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.
- Kappa are a type of water sprite found in Japanese folklore. In Shintō they are considered to be one of many suijin. A hair-covered variation of a Kappa is called a Hyōsube. Kappa are similar to Finnish Näkki, Scandinavian/Germanic Neck, Czech Vodník and Scottish Kelpie, in that all have been used to scare children of dangers lurking in waters. As their name would suggest, Kappa are capable of surviving underwater for extended period of times. Kappa kill their victims by "sucking" their insides out, leaving them "hollow".
- 1.03 Oh Kappa, My Kappa