Theresia Ray, a silver-haired operative for the criminal syndicate Mōryō, served as a disciplined agent under Kurara Tendō, her demeanor marked by emotional detachment and precise, formal speech. Born to a foreign father, she survived an abusive childhood, forging self-reliance as survival instinct. In her teens, a chance encounter in the Middle East led to a fragile bond with Hatsume Aoba, whose unexpected kindness clashed with Theresia’s guarded skepticism. Their connection shattered when traffickers abducted both, with Theresia resisting separation until captors subdued her violently. Manipulated into believing Hatsume’s family abandoned her post-ransom, Theresia embraced betrayal as truth, her trauma crystallizing into unwavering distrust that drew her into Mōryō’s ranks.

Years later, tasked with infiltrating Tsukikage, Theresia enrolled at Sorasaki High to surveil Hatsume. Reunions crackled with unresolved bitterness as she rebuffed Hatsume’s overtures. A confrontation at Hatsume’s home escalated when allies Momo Minamoto and Goe Ishikawa intervened, exposing Theresia’s simmering internal strife beneath her defiant facade.

Hatsume’s tactical bluff with a non-lethal neurotoxin during their duel pierced Theresia’s defenses, revealing vulnerabilities long buried. Subsequent revelations of Hatsume’s clandestine efforts to secure her freedom fractured Theresia’s loyalty to Mōryō. Defecting to Tsukikage, she collaborated to dismantle the syndicate’s city-wide brainwashing scheme, pivoting from adversary to reluctant ally.

Post-conflict, Theresia assumed a support role within Tsukikage, navigating cautious steps toward trust while retaining her reserved demeanor. Her journey—from isolation to fragile connection—mirrors a reckoning with childhood scars and the fraught path to reconciliation, her guarded interactions a testament to enduring wounds beneath her evolution.