Lightning, a disillusioned ex-soldier, becomes an unlikely fugitive when her sister is conscripted as a vessel for a divine force from Pulse and branded a traitor by Cocoon's ruling regime. The floating megastructure's government has declared a purge against all who've contacted the forbidden lower world, leaving Lightning desperate to rescue her sibling before execution. In her flight, she encounters other marked individuals—strangers bound by the same mysterious power—who are collectively entrusted with an enigmatic mission they must decipher together. As this fractured group evades the Sanctum's forces, they must race against a terrible fate: should they fail their incomprehensible task, they risk permanent transformation into something no longer human. Survival means understanding their purpose while staying ahead of both institutional oppression and supernatural corruption.