Hizuru Minakata returns to Hitogashima Island after fourteen years, compelled by the unresolved murder of her younger twin brother, Ryunosuke Minakata. Though authorities dismissed her suspicions, attributing his death to wild animals, the strangle marks on his body convinced her of foul play. His subsequent cremation prevented any further investigation, an event that profoundly shaped her motivations and psyche. She manifests a dual consciousness. Her primary identity is Hizuru: aloof, analytical, serious, and often expressionless. Under significant stress, particularly in combat or intense emotional situations, her personality shifts to embody her deceased brother, Ryunosuke. She adopts his name, mannerisms, and combat skills. This phenomenon, while superficially resembling dissociative identity disorder, originates from Ryunosuke's shadow data merging with her at his death. The identities share awareness but not memories; Ryunosuke relies on voice messages recorded by Hizuru to understand events when in control. Physically, Hizuru possesses violet eyes, straight black hair reaching her mid-back with short bangs, a fair complexion, and a distinctive beauty mark below the left side of her lips. She is notably tall with a pronounced figure. Her typical attire consists of functional black clothing: a suit blazer over a low-cut tank top, long pants, gloves, formal shoes, and often round-framed glasses. Her return coincides with Shinpei Ajiro's time loops. Initially distrustful, she allies with him after confirming his looping ability and their shared goal of eliminating the Shadows – entities that mimic and kill humans. She reveals critical Shadow information gained through years of hunting them and writing the allegorical novel "Swampman" under Ryunosuke's pen name: their true forms are vulnerable two-dimensional projections, they consume human "data," and their reproduction accelerates rapidly. During combat, Ryunosuke's persona manifests, granting enhanced reflexes, martial prowess, weapon mastery, and the ability to predict imminent dangers seconds in advance. Hizuru employs tools like hammers, shotguns, and customized phones to exploit Shadow weaknesses. She coordinates strategies with allies like the hunter Ginjirō Nezu, establishing communication protocols and contingency plans. Her arc culminates in confronting Shide, a centuries-old Shadow manipulating events. In later loops, Shide anticipates her tactics, leading to a fatal encounter where he impales her with a spear. In her final moments, she transfers her mission to Shinpei and Ryunosuke, dying resolved that they must stop Shide's ambitions. Across timelines, her core drive remains avenging Ryunosuke, though she demonstrates loyalty to allies and tactical adaptability. In a timeline where Shadows are prevented, Ryunosuke survives, and Hizuru continues writing, seemingly at peace.