Akira Fudo lernas de sia plej bona amiko Ryo Asuka ke demonoj reviviĝos kaj reakirus la mondon de la homoj. Kun homoj senesperaj kontraŭ tiu minaco, Ryo sugestas kombiniĝi kun demono. Kun tio, Akira iĝas Diabla Viro, estaĵo kun la potenco de demono sed kun homa koro.

Determined to protect his demon world from heavenly angels, demon Masatora Akutsu heads to earth in search of a charismatic human to rally his kin. Masquerading as a high schooler for his recruitment mission, he's captivated by the lovely Lily Amane. But he's in for a wild celestial surprise, because she's his archnemesis—an angel—and she's set on reforming his demonic ways!

A new guardian "angelus" uncovers a secret behind the Angelus System's bureaucracy that leads him to break its official rules about protecting humans.