In a dark and dangerous world where spirits and demons threaten humanity, Jay, a lonely and troubled teenager, becomes entangled in a supernatural battle for his life and soul. The story begins with Jay encountering Ellie, a ghost searching for her lost parents. Despite her spectral nature, Ellie becomes Jay's first true friend, and the two form a bond as they navigate a city teeming with danger.
Their journey takes a terrifying turn when a wolf-like creature hunts them down. Desperate to protect Ellie, Jay makes a fateful decision to accept the power of a mysterious and sinister voice in his head. This choice transforms him into a demonic version of himself, granting him incredible strength but at the cost of his humanity. With his new powers, Jay defeats the creature, but the demon within begins to take control, threatening to consume his soul entirely.
As Jay struggles with the darkness inside him, the exorcist Chiaki intervenes, determined to stop him. She believes the only way to save the city is to destroy Jay's heart, which the demon has claimed as its own. However, Ellie refuses to give up on Jay, risking her own safety to protect him. She believes in his ability to fight back and return to his true self.
While unconscious, Jay finds himself trapped in a crimson void, facing the demon that seeks to destroy his soul. Fueled by Ellie's voice calling out to him and his promise to help her find her parents, Jay discovers an inner strength he didn't know he had. He manages to not only resist the demon but also harness its power without losing control.
Alexander Moon is a new student at what seems to be just another boring high school. That is until he runs into an angel who attacks him. When everything seems to be over he is saved by a mysterious lightning wielding girl with black bat like wings. Once he awakens he finds himself surrounded by a very extraordinary group of people or rather devils who want him to join their school club. He soon finds out that these aren't your normal every day students. Enter the world of the supernatural. Devil's, Angels, and fallen angels alike battle but only the one with the Dark Heart can make the choice to save or destroy the world.