The weak teenager Akira Fudô has been protected by his best friend Ryô Asuka since they were children. When Akira's parents die in an accident, the family Makimura brings him to live with them, and Akira falls in love for the gorgeous Miki Makimura. When the father of Ryô accidentally opens a gate to hell in Antarctica, demons are released, merging with humans to survive. Akira hosts Aman and becomes Devilman but keeping his humanity while Ryô hosts Satan. The hysteria and panic replaces reason and mankind initiates a war against the demons, but destroying also themselves.