Jei is somewhat of an enigma. His true origin is unknown, but he claims to be a messenger from the gods, sent to seek out and destroy the evil in his world. No one is sure whether he really is a divine emissary or just a samurai that has lost all traces of sanity.

Besides his demonic eyes and chilling voice, adding weight to his argument is his apparent reincarnation after his first battle with Usagi Yojimbo. Discrediting his claim is the fact that he attacked Usagi, known for his noble and benevolent manner. Perhaps there is something buried within Usagi that is not apparent to those close to him.

Jei's body was seemingly obliterated by a lightning strike, yet he returned, some time later to kidnap Usagi's son Jotaro and gain his revenge on Usagi. Usagi prevailed once again on this occasion, with Jei being hurled over a clif, his own yari embedded in his side, however it is not known whether he was killed or not.

It seems he has been spotted alive and was after Usagi again because he believes that killing Usagi will make him a god. Insane or not, Jei seems to have at least some supernatural ability and is a master with the Yari. Few can stand against him.