After a disease destroys the human colony on the moon, Kyosuke Date and his mother flee to Earth, separated from their family. They take refuge in a cathedral, where his mother hides as a nun for reasons unknown to Kyosuke. When dangerous people discover their sanctuary, his mother stabs him before she herself is murdered. Days later, Kyosuke awakens alive in the home of a mysterious girl who claims to be his twin, Runa. Runa suffered a similar fate at the hands of her adoptive mother, but her soul was divided into several pieces, creating the so‑called “flicker girls” who are hunted by the evil Kirihara Group. Kyosuke survived because his DNA adapted to the disease.