According to an ancient legend, every three thousand years, a being known as the Ultra God is reborn—bringing harmony to the human, demon, and man-beast realms. Amanojaku, a man from the man-beast realm, has been searching for the Ultra God for hundreds of years, eager to witness the era of prosperity that the being will usher in. When Amanojaku's search leads him to Tatsuo Nagumo, a young high schooler enamored with chasing girls, it seems unlikely that the clueless student is really the fabled unifier of realms. However, as forces from the demon realm also take notice of Nagumo, it becomes unclear whether the Ultra God is a force of peace or ultimate destruction. [Written by MAL Rewrite]