In Japanese folklore, an Ikiryoh is a spirit born from evil thoughts and feelings harbored by a person.
Ikiryoh are energized by hatred. When it becomes powerful enough to leave its source it enters and possesses the person, or animal, etc. the original source hated.
Once it is inside the victim, it will drink all of their energy slowly. Ikiryoh is very difficult to exorcise. To drive the spirit away rights read from the Buddhist sutras are used.
Image from Google search
Interesting! In my book, The Grimhold Wolf, willy-wisps were created by ill wishes that were undeserved. Because the victim was innocent, the curses couldn’t take hold, so they roamed the world as a sort of undead. Sounds like the Japanese had a similar idea.
I love that idea, Deby!