After rebelling against divine orders, Lucifer, a fallen Archangel, plummets from Heaven and lands in a high school church, caught between realms. Witnessed by Maria, a gentle academy student, Lucifer descends to Hell. There, she teams up with Leviathan, an aspiring Demon Lord, to challenge the ruling authority, the Seven Sins, led by Belial. Despite their efforts, the Seven Sins overpower Lucifer, binding her powers with a Garb of Punishment and transforming her into a Demon Lord. Seeking retribution, Lucifer, now accompanied by Leviathan, returns to Earth and compels Maria into servitude. Together, they embark on a quest to defeat the Seven Sins and break the curse of the Garb that shackles Lucifer's true nature.