Tetsu Totsumura is the only police officer on Hitogashima, known for his lighthearted and approachable demeanor. He is maternally related to the Kofune family, embedding him within the island's community. He possesses messy orange hair and consistently wears his police uniform with yellow-tinted sunglasses. Tetsu frequents Kofune's diner, habitually ordering "the usual." Early iterations see Tetsu attend Ushio Kofune's funeral and later inform Mio Kofune of the Kobayakawa family's disappearance, suggesting debt as the motive. In the second iteration, Shadow Mio kills him with a kitchen knife near her home; his shadow duplicate immediately replaces him. Shinpei Ajiro prevents this encounter in the third iteration. Here, Tetsu investigates the Kobayakawa disappearance, learns of an incoming detective, and fulfills Ushio's final request by delivering a phone to Shinpei. During the fourth iteration, following Shiori Kobayakawa's shadow to a manhole, Tetsu accompanies Mio and the shadow into the sewers after Mio suggests it could impress Erika. Inside, they find the injured Ryunosuke Minakata. Tetsu carries Hizuru Minakata deeper into the caves but is fatally shot by a shadow after revealing he dropped his gun. In later iterations, Tetsu joins the resistance against the shadows. He witnesses Ushio's memories at the elementary school and agrees to fight alongside other residents. Hizuru questions his presence during the eighth iteration but provides him a firearm. He then aids Tokiko Hishigata's escape with Ginjiro Nezu. His final appearance occurs in the ninth iteration, witnessing Hizuru's death after her battle with Shide. His name, Tetsu (哲), means "philosophy," while Totsumura combines "convex/uneven" (凸) with "town/village" (村).