The father of Shuya Nanahara is never given a name in Battle Royale and appears only through backstory and memory, since he is already dead before the main events of the story begin. The exact circumstances of his death differ across the various versions of the tale. In the film adaptation, Shuya's mother abandoned the family when Shuya was in fourth grade, and his father, who suffered from mental problems, hanged himself; Shuya discovered the body when he came home on his first day of seventh grade. In the original novel, the details are told somewhat differently: some accounts describe both parents dying in an automobile accident when Shuya was five years old, with rumors that the accident was tied to anti-government activity, while other tellings state that his father was killed by the regime for opposing it and that his mother died when Shuya was in third grade. The manga similarly suggests that his father was killed for resisting the government and that his mother died some time afterward.

Because the father dies before the narrative begins, he has no active role in the events and lacks any on-screen personality, development, or abilities. His importance lies entirely in what his death causes. After losing his parents, no other relatives were willing to take Shuya in, and he was placed in an orphanage, where he formed the friendships that define him. The manner of his death, whether through suicide or state violence, left Shuya with a lasting sense of loss and instability, and it ties directly into the story's broader themes of an authoritarian government that destroys families and rules through fear. In the sequel, the memory of losing his family becomes part of what drives Shuya to fight against the adults who uphold the system that forces children to kill one another.

His relationship with Shuya is shaped entirely by absence and grief. Discovering the death of a parent is a formative trauma for Shuya, contributing to his empathy, his wariness of authority, and his strong need to protect the people he cares for. Losing his father also helps explain why Shuya, having already been stripped of his family, remains willing to trust his classmates and refuses to accept the logic of the killing game. In essence, the father serves as a motivating backstory element rather than a developed character: his fate accounts for Shuya's orphaned upbringing, his emotional wounds, and his eventual opposition to the system that took his family from him.