Neko-ken.
However, what has never been explained is who exactly created such a bizarre technique, and why. These people still exist, and they have taken a decided interest in a certain pig-tailed martial artist. For what reason remains to be revealed.
This is a tale by Madamme Hydra, and she puts it aptly; "A demon story with romantic interludes . . . . . . or perhaps a love story with demonic complications."
Part 1: No More Pussyfooting Around
Part 2: Damage Control
Part 3: Harbingers of the Storm
Part 4: Visitations
Part 5: Darkening Hearts: Part I
Part 6: Darkening Hearts: Part II