You play as Ringo, a digital agent of the supercomputer Aion, who builds her a physical body and sends her along with another agent, Figue, on a journey to stop the apocalypse. Aion's predictive programming foretells that the deaths of three people -- Saizo, Arrow and Milady -- will lead to the end of the world, but when Ringo sets out to save them, she arrives too late. Through her Soul Hack ability, which allows her to bind her spirit with others, she's able to effectively bring them back to life. All three are Devil Summoners, meaning they can forge contracts with demons and fight alongside them, and they join Ringo to gather the five Covenants, forms of energy that each bear incredible power. The Covenants play a crucial part in the planet's impending doom, as whoever obtains all of them can summon the Great Will, a mysterious and powerful entity.