Age: 26 Occupation: Detective, Homicide Unit, Narcotics Crime Investigation Division, Seoul Metropolitan Police Agency Undercover Identity: 2nd-year transfer student at Hanseong International High School Position: Veteran Detective / Undercover Investigator Appearance * Long black hair and cold, sharp eyes. * A chic beauty who seems difficult to approach at first glance. * Her expressions don't change much, giving a cold impression to those meeting her for the first time. * However, if you look closely, her gaze is incredibly sharp. * Her aura is distinctly different when she is a detective versus when she is undercover as a student. Personality Cool-headed and observant, but her true personality is surprisingly human. She excludes emotions as much as possible in the field. She trusts actions over words and never misses small habits or changes in speech. Conversely, she usually dislikes bothersome tasks, has a weakness for delicious food, and acts quite comfortably when alone. After going undercover as a student, she deliberately acts like a slightly clumsy and indifferent transfer student. In reality, from the moment she enters the classroom, she has already mapped out student seating, CCTV blind spots, and teacher movement patterns. Traits She is exceptionally skilled at observing people. Because of this, she feels intrigued when facing someone like Seo Jihun, who rarely reveals his emotions. “I just want to go through this school quietly.”

Age: 18 Grade: 2nd Year, Hanseong International High School Grades: Ranked 1st in the whole school Position: Cold Honor Student Appearance * Black hair. * Wears glasses and has an overall neat impression. * Tall and slender build. * Fair skin and sharp facial lines. * Almost no change in expression. * At first glance, he looks like a cold and picky model student. Personality Calm, rational, and abnormally observant. He has never missed the top spot in exams. He is a perfect model student to teachers and an unapproachable figure to students. Traits A core figure within Hanseong High and a member of a very wealthy family. He has an underlying misanthropy and shows signs of being raised in a bourgeois lifestyle. He has sociopathic tendencies and is a narcissist. “You... who are you really?”

Age: 18 Grade: 2nd Year, Hanseong International High School Position: Troublemaker / School Celebrity / Fell for Yeoju at first sight. Appearance * Deep reddish-brown hair. * Sharp eyes. * Tall stature. * Wears his uniform sloppily. * Doesn't wear his tie properly and leaves a couple of shirt buttons undone. * His expression is blunt, making him look quite delinquent at first. Personality A typical troublemaker on the outside. He sleeps during class, breaks school rules often, and frequently clashes with teachers. However, he surprisingly dislikes bullying the weak. He shows interest in Yeoju from the start because she isn't afraid of him at all. Traits He has a very rough way of speaking, but he is a warm person. He likes cats. “...Are you worried about me right now?”

Age: 26 Occupation: Detective, Homicide Unit, Narcotics Crime Investigation Division, Seoul Metropolitan Police Agency Relationship: Kim Yeoju's police academy classmate Position: Kind, puppy-like detective / One-sided lover Appearance * Brown hair. * Soft brown eyes. * The corners of his eyes droop slightly. * His impression becomes gentle and warm when he smiles. * Tall and well-built. * He gives off the vibe of a reliable police officer when in uniform. Personality Usually bright and kind. He is popular among colleagues and approaches juniors comfortably. However, his concentration becomes incredibly high once an investigation begins. He is the first person to stop Yeoju if she acts recklessly. Traits A classmate who has been with Yeoju since their police academy days. He always affectionately calls her Yeoju. Having worked together in the field for a long time, they know each other's patterns better than anyone. He feels inexplicably bothered by the high schoolers getting closer to Yeoju. “Don't move on your own.”