Devilman: Youchou Sirene-hen

Demons exist and their power is beyond what humans can fathom. In fact, they are so strong that humans do not stand a chance against them in a fight. <br><br> The only thing strong enough to defeat a demon is another demon, and it is through this logic that Ryo Asuka hatches the plan to have his good-hearted friend, Akira Fudo, possessed by a demon. If a person is of pure of heart, then they might be able to control the demon that possesses them, and thereby acquire power equal to a demon. After raising some hell in a club, the plan works, and Akira is possessed by the powerful demon known as Amon. <br><br> Now Akira is humanity's sole champion of justice against the hidden demon menace that has plagued humanity since the dawn of time. <br><br> (Source: Anime News Network)