In a city known as the Demon's Gate, high school student Masato Kawashima endures a brutal series of tragedies. His mother is murdered by a thug, and three months later he is robbed and beaten within an inch of his life. As he lies dying, a demon appears before him and offers a stark choice: die now and go to heaven, or sell his soul, survive, and burn in hell later. Masato chooses to sell his soul, gaining the demon's power and a cursed immortality in exchange for his eternal damnation. Now bound to a demonic contract, he must navigate a world where supernatural forces are real and hidden within the city's underworld. Cursed to live forever with his newfound strength, Masato sets out to confront his destiny and uncover the truth behind the demons that haunt the streets. The story follows his violent journey as he battles other demon-possessed individuals, questions the nature of his own soul, and seeks the deeper secrets of the city that the demons call home.