Grudge

About

A vengeful spirit intent on finding out his true identity, going so far as to trick Asahi into forming a contract with him, thus binding the two together and allowing them to share the same body.
If granted permission, he can take control of Asahi's body.

He has tremendous power that manifests itself in the form of endless black smoke, which he can manipulate to take the shape of weapons or to heal wounds. He is also capable of imitating others' techniques, be they of combat or magic, just by observing them once.