Zenki (1995)

Chiaki Enno is just your average high school student, who spends her spare time studying to be a Shinto exorcist. One day, however, the forces of evil are unleashed in her backyard. Quite accidentally, she summons Zenki, the most powerful of demon lords. Zenki trashes the evil forces with aplomb... and then tries to attack Chiaki! Unfortunately, he's her "shikigami"-- spirit familiar- and therefore unable to attack her. So, he reverts to his normal form: a loudmouthed, obnoxious, bratty little kid...