Kyōsuke Irie grew up impoverished yet aspired to become a doctor, earning the childhood nickname "Doctor Kyōsuke-kun" from neighborhood role-playing. His parents—a construction worker and sensitive homemaker—funded a celebratory party upon his acceptance into a prestigious Tokyo medical school. During college, Irie learned of his father's sudden violent outbursts, later attributed to organic brain syndrome from a work-related frontal lobe injury. After his mother fled the abuse, his father died in a street fight before Irie could intervene. This trauma drove him to specialize in neurosurgery and psychosurgery, focusing on conditions like his father's. Gaining recognition as a "young genius" for successful lobotomies, his methods faced criticism over high failure rates. When lobotomies were banned, Irie continued unauthorized procedures, convinced they were mental illness's only solution, leading to his expulsion from the medical community. This background drew the attention of "Tokyo," a secret organization recruiting him for Takano Miyo's Hinamizawa research group. As nominal director of the Irie Clinic in Hinamizawa, he served as a figurehead for research into Hinamizawa Syndrome, with Takano wielding actual authority. The clinic masked syndrome studies, and Irie was designated to take blame for operational failures, resulting in his suicide via sleeping pill overdose in catastrophic timelines like Tatarigoroshi-hen and Minagoroshi-hen. Concurrently, he coached the village baseball team, the Hinamizawa Fighters, earning villagers' respect while remaining unaware of Takano's deeper schemes until Matsuribayashi-hen. Irie maintained complex relationships: he administered regular injections to suppress Hōjō Satoko's syndrome symptoms, having once considered dissecting her for research before an experimental cure stabilized her. He developed an inappropriate fixation, joking about marrying Satoko and encouraging maid outfits, drawing criticism from colleagues like Chie Rumiko. For Satoko's brother Satoshi, Irie induced a pharmacological coma after terminal-stage syndrome developed post his aunt's murder, concealing Satoshi in the clinic's basement for years and revealing it only to Shion Sonozaki in Matsuribayashi-hen. His professional dynamic with Takano included unethical collaborations like vivisecting a terminal patient at her suggestion. Irie remained ignorant of her role in orchestrating tragedies until Rika Furude exposed her in Matsuribayashi-hen, prompting him to ally against her. He also shared a friendly rapport with Tomitake Jirō, never suspecting Takano's involvement in Tomitake's repeated deaths. Physically, Irie appeared tall with light brown center-parted hair, green eyes, and distinctive oval glasses. He wore a black vest, gray collared shirt, yellow tie, and lab coat professionally; a yellow shirt with white pants casually; and a red-white-yellow baseball uniform as coach. Originally conceived as a ruthless antagonist—a "demon of a man" who would reveal Satoshi's preserved brain to Satoko—negative feedback reassigned this role to Takano, redesigning Irie as morally ambiguous yet redeemable. This villainous iteration later emerged as Dr. Hiroaki Nitta in the spin-off *Hinamizawa Bus Stop*. In arcs like Matsuribayashi-hen, Irie confronted his research complicity, dedicating himself to finding a true syndrome cure. He reappeared in the *Rei* manga set thirty-five years post-original events, still participating in village activities.