Jinpachi Shimada, a high school student and close friend of Kenta Kogure, is one of ten individuals lured to an abandoned school building via mysterious letters. Alongside Kenta, Kotomi Asakawa, Rika Akagawa, and others, he initially aids escape efforts by searching for keys and scouting rooms for useful items.

As tensions escalate, Miyuki Sakaki grows suspicious of Jinpachi, accusing him of colluding with Isaku—the janitor imprisoning them. This suspicion confirms Jinpachi’s role as Isaku’s mole, a betrayal that heightens the group’s peril and drives the narrative’s conflict.

Jinpachi’s disappearance during confinement directly influences the story’s climax. If unrescued before the group reaches the first floor, Akemi ignites the building, killing all. In scenarios where Isaku retains captives, Kenta graduates with survivors but mourns Jinpachi and others who vanish permanently from the school.

His involvement remains consistent across adaptations: the original visual novel and 1997/1999 anime OVAs. As a catalyst for conflict tied to Isaku’s schemes, Jinpachi underscores themes of trust and deception.