Freshly cast out of Heaven, the former angel Lucifer makes a brief stop in a high school church on Earth, where she encounters a girl named Maria Totsuka before continuing her fall to Hell. Once there, she is met and fawned over by Leviathan, an aspiring minor Demon Lord, and challenged to combat by Satan and Belial, two Demon Lords of the Seven Mortal Sins and members of the ruling council of Hell who accuse her of intending an invasion of their territory. Despite gaining the upper hand initially, Lucifer is eventually subdued by Belial and stripped of her angel ...
The gang travels to London to face another Mortal Sin, the Demon Lord of Greed. Maria finds a strange shop that sells a potion that purports to grant anyone their wildest desires. Lucifer makes haste to the shop, only to quickly fall into a trap!
After taking down each of the Mortal Sins, Lucifer returns to the Gates of Hell as a true Demon Lord with millions of followers. With little time, she must make her way to the throne and save Maria. That is, if she can survive the ferry ride!
With big plans to swap Heaven and Hell, Lucifer makes her way through the Circles of Hell. Meanwhile, though Belial has the Mortal Sins on her side, she'll make them pay for their betrayals! With her cruel torments, will she make them submit?
Captured by Belial, Lucifer takes hit after hit in order to get the answers she seeks. But instead, she learns that Belial is a fallen angel. Cast out by Lucifer, Belial has held on to her grudge and plans on finally exacting her revenge-by using Maria!
It's Heaven versus Hell in this final showdown! Unable to deal with Heaven's betrayal, Belial attacks the angel Michael before being cast to Earth. Bearing the Demon Lord title, Lucifer and her Mortal Sins wage war against the angels.