A demon wakes to obliterate the world and unite men, man-beasts and monster demons. Legend has it that once every 3,000 years, a supreme being known as the Choujin, or “Overfiend”, makes his appearance on Earth to unite the realms of the human, Makai (demon) and Jūjinkai (half-man, half-beast) races in peace and harmony. Amano Jyaku, a Jūjinkai, discovers that high school student Tatsuo Nagumo may be the incarnation of the Choujin, and must protect him at all costs from minions of the Makai.