According to oneiromantic theory, dreams of dragons symbolize the struggle of losing oneself to anger. Fittingly, Souya Kuroi awakens from a nightmare in which a colossal dragon destroys everything around him in a blaze of rainbow-colored light. After learning that he lost his parents and his memory in a strange accident, the waking world itself becomes a nightmare. With this dream as his only memory, he has no choice but to rely on his two peculiar guardians: the energetic and spunky maid Ginko, and a giant cat known only as "Sensei." His new life is upended when the residents of Saromisaka City are attacked by a teddy bear-shaped UFO. When military force proves ineffective, seven mysterious individuals rise to battle the monstrosity. These heroes destroy the invader in a flurry of rainbow-colored light—the same light Souya witnessed in his nightmare. With the alien threat repelled, these seven strangers face a new adversary: Souya. Vowing vengeance on those who ruined his former life, he launches a crusade against these "heroes" and becomes entangled in a conflict of galactic proportions.