A high school has achieved a remarkable claim: two thousand days without a single incident of bullying. This is made possible by a combination of exceptionally dedicated teachers and an all-encompassing surveillance system that monitors every hallway, classroom, and even students' school-issued smartphones. Into this seemingly ideal environment steps first-year student Kiyokazu Kizuna, a boy who fully supports the school's anti-bullying policies and actively participates in its enforcement. At this school, he reunites with Shijo Kahori, a former classmate who was severely bullied during middle school. In this supposedly safe haven, the two begin to grow closer, with Kiyokazu seeing the school's system as a chance for Shijo to finally find peace.

The fragile normalcy shatters when Kiyokazu discovers that Shijo has, in fact, been suffering from bullying once again. Immediately after this revelation, Shijo falls from the school rooftop. The administration swiftly rules her death an accident, but Kiyokazu cannot accept this conclusion. Haunted by the discrepancy between the school's flawless image and the reality he glimpsed, he begins his own investigation. He is joined by a brash but loyal delinquent nicknamed Yattsun, who, despite his rough exterior, was also shaken by Shijo's death. Together, they infiltrate the school's central monitoring room, a place known among students as the "watching room," and review the security footage from the roof. What they find there suggests Shijo's fall was not an accident.

As Kiyokazu and Yattsun dig deeper, they realize the school's perfect record is a carefully maintained illusion. By approaching the art club that Shijo belonged to, they meet a student named Momota who may know the truth about the day of the incident, but she herself becomes a target of suspicion and possible bullying. With the help of a stern disciplinary committee member named Terui, they close in on a prime suspect: a girl named Tanaka Nanane, who had tormented Shijo in middle school and now appears to have been involved in the graffiti defacing Shijo's artwork. Yet, as the investigation progresses, it becomes clear that the truth about the school's zero-bullying promise runs far deeper than a single culprit. The school's administration is actively burying the evidence, and the students who seek the truth find themselves challenging a system designed to protect its own reputation at any cost.