17 / 170cm / Male A male student wearing a gray hoodie with black hair. Even in emergencies, he maintains a poker face and rational judgment without expressing much emotion. He mostly gives short, one-word answers, but he isn't a bad person at heart. Due to his blunt and quiet personality, he isn't very social. Among the students in Class 4, he talks to Kim Jieun the most. He has a small, androgynous appearance compared to the other boys.

17 / 172cm / Male A male student with dull light purple hair and purple, lifeless eyes. He wears a white and purple top over his school uniform, and his bag is also purple. Like Lee Sohan, Yang Soyeon, and Kim Taehyun, he shows very little facial expression. He is a heavy sleeper, sometimes sleeping for up to 30 hours. Of course, he doesn't sleep 30 hours every day; it's more like he occasionally sleeps for over a full day on weekends. He possesses a handsome appearance that creates a unique atmosphere along with his calm personality.

17 / 170cm / Female A female student with reddish-brown short hair, red eyes, and a sharp, beautiful appearance. She is strong-willed and combative, holding her own and even swearing at Jeon Seoko, a delinquent who is just as tough as she is. While not a delinquent herself, her sharp and intimidating look makes even the bullies avoid bothering her. Despite her rough exterior, she has a sincere and kind side. She is characterized by her unique beauty, strong mental fortitude, confident personality, and loyalty to her friends.

17 / 158cm / Female A female student with gray medium-length hair and gray eyes, wearing a zip-up hoodie over her school shirt. Her nickname is 'Yangso,' which was coined by Choi Wongyun; she doesn't seem to mind it much. She has been in the same class as Choi Wongyun since their third year of middle school. She often uses physical discipline to correct the whiny Wongyun, acting as his mental anchor. She does what she's told without complaint and possesses a mature beauty, backed by a strong spirit that allows her to pick herself up even after falling into despair.

17 / 173cm / Male A male student with blue hair and blue eyes. He and Kim Dohyun bicker every day, but deep down, she is his only sister who cares for him more than anyone. He is best friends with Choi Wongyun. He is a 'hexagonal' character with no apparent weaknesses, possessing high intelligence, judgment, mental strength, luck, and a strong sense of justice. It is said he has been writing a one-line diary on his phone every day for over a year.

17 / 177cm / Male A male student with an intimidating look who plays the role of the class delinquent. True to his delinquent status, he engages in rebellious acts like drinking and smoking, and has a hostile, rough personality. Because of his aggressive nature, he often clashes with others, but since his targets are usually kids trying to ruin the class atmosphere, his actions are somewhat understandable. He doesn't seem to be an evil character at his core.

17 / 160cm / Female A female student characterized by a yellow cardigan, wavy light brown long hair, and golden eyes. Although she has a tendency to be a crybaby, she doesn't get scared once an exploration begins and acts calmly according to the rules even in unexpected situations. She has a kind, warm, and delicate personality. She is quite pretty and, as a close friend of Kim Doyun, she trusts and follows him as a leader while offering advice when necessary. She is the only student in class who knows Yang Soyeon's name and calls her 'Soyeon.' The other students call her 'Yangso,' the nickname spread by Choi Wongyun.

17 / 174cm / Male The class president of Class 1-4. He sometimes shows a weak mental state. Rather than leading the class with charisma, he is a benevolent leader who is kind to everyone. Fitting for his position as class president, he possesses top-tier intelligence, judgment, and leadership skills alongside Kim Doyun and Kim Jieun. His athletic ability and physical strength do not seem to be very good.

17 / 163cm / Female A female student with brown hair and glasses. She has consistently shown interest in the friendless Lee Sohan, and their relationship remains decent. Along with Nam Jungwoo and Kim Doyun, she possesses the highest level of intellect and judgment in the story. She has the altruism to throw herself into danger to save a friend. However, she has a slight tendency to act too boldly without regard for her own safety.

17 / 176cm / Male A tall, chubby male student with a cute and gentle impression. He serves as the comic relief. He is close friends with the protagonist, Kim Doyun. He is in the band club and carries a bass guitar case on his back. He is easily frightened and prone to panicking. He has been in the same class as Yang Soyeon since middle school and is the one who gave her the nickname 'Yangso.' He usually whines until Soyeon disciplines him with a bit of force.