In a post-apocalyptic world, "The World" is a force for good. Though no one knows where it is, it has been watching over Earth for so long that war has become a myth. The goal of the airship Norn is to transfer nine ability users to The World. Norn departs after collecting the final individual. Eight men and three women are onboard, including Koharu, who has finally escaped her loneliness and despises her destructive power; Mikoto Kuga, born into a noble family, who uses her barrier skill to protect the Norn and those it carries; and Nanami Shiranui, whose ability only causes pain and who wishes to die for a past sin she has committed. When passengers discover there are too many people on the plane, they get suspicious.