Akira Fudo, known as Devilman, emerges in the crossover *Mazinger Z vs. Devilman* as a hybrid entity merging a demonic physique with a human psyche. Defying his origins as a rogue member of the Demon Tribe, he thwarts their schemes to eradicate humanity. When the demon Sirene flees after clashes between Mazinger Z and Aphrodite A, Akira awakens his Devilman form to hunt her down.

Dr. Hell forges an alliance with the Demon Tribe, releasing them from Himalayan captivity and arming them with neural-control technology. Disguising himself among them, Devilman exposes their pact and alerts Koji Kabuto, Mazinger Z’s pilot. Their rivalry ignites when Devilman taunts Mazinger’s flight limitations, sparking a high-speed motorcycle duel. Reluctant allies, they unite against Dr. Hell’s escalating threat.

During the assault on the Photon Power Laboratory, Devilman intervenes but falters against overwhelming forces, captured and tortured on a glacial cross as punishment for betrayal. Koji repairs Mazinger Z’s Jet Scrander, soaring to free him. Their combined might demolishes Dr. Hell’s fortress, though the villain escapes. The film ends with Devilman and Koji departing as allies, vigilant against the Demon Tribe’s lingering menace.

Devilman wields bat-like wings for flight, superhuman strength, and combat mastery. His narrative arc underscores rebellion against his demonic nature and sacrificial resolve to shield humanity, framing a tale of uneasy alliances, redemption, and collective defiance against annihilation.