Ryo Hamura, a second-year Oumidai Private Academy student, navigates solitary life in Otsuna City after his parents’ relocation abroad. His routine existence fractures when supernatural forces draw him into a covert war against the Light Hunters, enigmatic entities threatening humanity. Recruited by an extraordinary faction, Ryo wields the power "Repeat"—a kinetic mimicry ability enabling precise replication of observed movements to outmaneuver adversaries. His signature weapon, the Formless Sword, shifts its structure mid-combat, adapting to tactical demands.

Initially an unremarkable teenager, Ryo’s latent potential ignites through rigorous training and alliances, positioning him as pivotal to thwarting the apocalyptic "azure night of eternal despair." Bonds with companions, such as a crimson-eyed ally who rescues him during a critical assault, catalyze his evolution from reluctant participant to determined protector. These connections ripple across narrative timelines, with alternate iterations depicting his psychic awakening during a monstrous confrontation—an event that alerts supernatural organizations to his value.

A year of independence prior to the conflict underscores his self-reliance, though no prior encounters with the supernatural are documented. Multifaceted storylines chronicle his dual existence: managing academic obligations while honing combat strategies, allocating skill enhancements, and refining his morphing blade. The narrative threads examine his combat ingenuity, emergent command instincts, and fluctuating dynamics within a team of gifted peers, with diverging outcomes shaped by pivotal decisions across adaptations.