In the tumultuous life of 16-year-old Setsuna Mudo, navigating high school bullies is just one challenge. Complicating matters is his forbidden love for his sister Sara, whom he rarely sees. However, his reality takes a surreal turn when he is confronted by enigmatic angels and demons. They reveal conflicting truths about his past, with angels insisting he is the revered Alexiel reborn, while demons claim he once led a rebellion against God. As Setsuna grapples with his unearthly heritage and the looming clash between Heaven and Hell, the specter of an impending celestial war hangs heavily over his uncertain future.