Jin Tachibana exists as two distinct entities. The original Jin possessed telekinesis requiring visual contact with targets. He had indigo hair, olive eyes with cat-like pupils, and wore rectangular glasses. His personality combined softness for animals with indifference towards most people and a sadistic streak enabling him to kill classmates without remorse during the island conflict five years prior. He formed a significant bond with Rin Onodera, saving her multiple times and shielding her from cannon fire during the talented students' civil war. This protection caused a head injury that later resulted in a delayed cerebral hemorrhage, leaving him comatose. Before losing consciousness permanently, he urged Rin to seek revenge and "become somebody kind." He remains comatose under back-alley doctors' care.

The individual commonly presenting as Jin Tachibana is an imposter, revealed to be Rin Onodera using transformation abilities. This imposter's true appearance, name, and gender remain concealed; the form of a young man with dark hair, glasses, and a suit is a deliberate transformation. The core talent is shapeshifting, allowing transformation into any living creature and full replication of their talents, provided the transformation occurs unseen. Limitations include inability to transform while observed, incapability to assume the form of non-talented individuals or deceased persons, and potential loss of control over copied talents. Initially unable to transform into individuals with certain nullification talents, this limitation was later overcome with unspecified consequences. The imposter employs distractions to create unseen transformation opportunities.

Rin adopted Jin Tachibana's identity following his coma. Stranded on the island after the civil war five years ago, she attempted to return to the mainland only to discover the government had declared her deceased. Survival attempts on the mainland led to life-threatening encounters, forcing her return to the island where she assumed Jin's form and resided. This imposter Jin observed Nana Hiiragi extensively, often disguised as animals, and approached her by impersonating Michiru Inukai. Nana detected inconsistencies in speech and an unexplained wrist injury, exposing the ruse. The imposter demonstrated detailed knowledge of Nana's murders. Personality-wise, this Jin is highly perceptive, cunning, and strategically adept, matching Nana in wit and frequently engaging in confrontations. Motives remain enigmatic, though interactions suggest a willingness to exchange information for mutual benefit and a declared intent to eliminate perceived threats like Nana.

The connection stems from the island's past. The real Jin protected Rin during the deadly student conflict five years ago. Their relationship evolved into a survival partnership, with Jin handling combat while Rin transformed into animals. After Jin's injury and coma, Rin transported him off the island using a boat, shifting between his form and a bird for navigation and vigilance. She assumed Jin's identity permanently following this event, driven by his final request for revenge and identity. The imposter Jin's actions and investigation into the mysterious committee are linked to this history and the unresolved circumstances surrounding the island and the talented.