As demons start possessing human bodies, only the strongest individuals survive. When Miki Makimura, a young witch in training, asks her friend Akira Fudou for assistance with a ritual, the spell is cut short, leaving Akira on the verge of death. His body is then taken over by a powerful entity named Amon. Now caught between his humanity and the demon inside him, Akira employs his powers to fight in the war between demons and humans for the future of the world itself!