Tonton Streaming Undercover High School (2025) S1E6 - Hye Seong's Father's Notebook

The school's security guard dies, leaving Hae Seong a notebook belonging to his missing father. The revelation is shocking, and he storms the NIS for answers. The answer pushes him away from the mission, and he takes time off. However, he resolves to continue but returns only to discover Su A witnessed it all