Devilman is a movie based on the manga by Go Nagai. It tells the story of a teenager who becomes Devilman, a superhero with demonic powers. He fights against various monsters to protect humanity from evil forces. The movie explores themes of horror, action, fantasy, and thriller.

In Ikebukuro, unbeaten street fighter Ran Sakurai (Yosuke Kawamura) and his friend Kenji (Yosuke Asari) run a benriya operation called "Randys" to earn enough money to buy a haka for their dead friend Shinichi Hoshi (Tsutomu Takahashi). Randys is named after their hero, Randy Bass: the American baseball player who helped lead the "hard luck" Hanshin Tigers to a Japan series title in 1985. A benriya is basically a problem-solver that accepts payment to do anything you need done, and Randys specializes in helping the weak triumph over the strong, much like Randy Bass did with Hanshin. One day, they find out the feared leader of a team of badasses called (appropriately enough) the Giants, Takeshi (Hisato Izaki), has returned to Ikebukuro to stir up trouble. He has only one goal: to beat the crap out of Sakurai. A dispute that began 4 years ago is about to be settled, but not before the streets of Ikebukuro are covered in blood...

Following his release from the reformatory, Hayato is a free man and begins working at a Korean host club, the same one Yoshio works at. Unable to handle the woman and work he immediately wants to quit. However, Yoshio soon ends up saddled with a large debt a customer has made and is forced to pay with his life in an illegal underground fighting match. To save Yoshio, Hayato enters instead and comes up against Honda an ex-pro boxer.