Hiroshi Utsui is a student who serves as the primary antagonist in his school environment. Outwardly, he presents a charming and agreeable manner, but this facade conceals a deeply nasty and bullying nature. He is always looking for vulnerable targets to exploit and takes pleasure in manipulating and controlling others.

His primary motivation stems from a desire for power and domination over those around him. When a new and inexperienced teacher named Machiko Natsukawa joins the school, Hiroshi identifies her as the perfect victim. He steals her underwear and then refuses to return it, using the theft as leverage to blackmail her. His goal is to force her into submission, making her comply with his demands and turning her into a tool for his amusement.

In the story, Hiroshi is a catalyst that helps plunge the school into chaos. He does not act alone, as his class is filled with other students who have various predatory and disturbed tendencies. Together, they create a situation where Machiko Natsukawa is drawn into a cycle of exploitation from which she cannot easily escape. Hiroshi’s actions are central to the collapse of order within the classroom.

His key relationship is with Machiko Natsukawa, his teacher, whom he systematically blackmails and abuses. He acts as the ringleader among his classmates, which includes other bullies, a sexually disturbed nerd, and a mysterious girl, using the school’s network of spy cameras to control the narrative and exploit others.

Information regarding Hiroshi Utsui's personal development throughout the narrative or any notable special abilities he might possess is not available.