Devil Man: The Birth, Demon Bird OVA (DVD) (Japanese Animation)

The Birth:

Akira Fudou leads the life of a typical high school student. After a chance encounter with school bullies, he is rescued by his childhood friend Ryou Asuka. Ryou and Akira catch up over the course of an afternoon that ends with them crashing a party at a nightclub. Initially uncomfortable with the environment, Akira is shocked when violence provokes some of the club’s partygoers to transform into demonic monsters. He and Ryou are only saved from the encounter thanks to the intervention of a great demon known as Amon. Amon possesses Akira, and the two together form the powerful Devilman⁠—a being that, due to the influence of Akira’s strong empathy for his fellow man, is resolved to keep the human race safe from the threats of demonkind.

The Demon Bird:

After Akira Fudou fused with the demon Amon to become the being known as Devilman, he has struggled with striking a balance between his human heart and his new violent tendencies. However, as other demons become aware of him and wreak havoc on the lives of those he cares about, Akira has little choice but to fight them tooth and nail. As he fights Jinmen, a turtlelike demon with living human faces embedded in his shell; and Sirene, a fearsome winged demon, Akira must use every scrap of his strength if he is going to stay alive.