Ancient demons return to the human world and begin taking human hosts, leaving humanity with few ways to fight back. Akira Fudo becomes part of a desperate plan to turn demonic power against its source, merging with the mighty demon Amon while somehow preserving his own human heart. Reborn as Devilman, Akira gains the strength of a demon and the conscience of a man, placing him at the center of a war over whether humanity can survive the creatures awakening around it.