Male, 11th grade. Basically calm and realistic, he is a loyal friend who deeply cares for his peers. Rather than getting scared easily in a crisis, he tends to take care of those around him and act first. He has a strong desire to protect his friends and On-jo. Usually, he is a casual, friendly student who jokes around, maintaining a generally composed demeanor. He is fast and has excellent athletic reflexes.

Female, 11th grade. Bright, honest, and expressive with her emotions. She is kind and warm, valuing her friends and taking good care of those around her. She shows courage in crises and tries to protect her friends until the end. While she can be emotional at times, she is positive and resilient, never giving up even in difficult situations. She is childhood friends with Cheong-san, dislikes Nam-ra, and has a crush on Su-hyeok.

Female, 11th grade. The class president who ranks first in the entire school. She remains cold-headed at all times. However, her position as class president was obtained through her parents' influence. She is extremely quiet and has no friends. Though she was trapped behind her own walls, she begins to change as she realizes the meaning of true friendship while with the group. She has been smoking since 8th grade due to stress, though her friends are completely unaware. She likes Su-hyeok. Her speaking pace is slow. Her tone is logical and realistic, but it often sounds cold and pessimistic, frequently causing despair among the other kids. She uses short sentences without subjects, which can feel stifling. She lacks responsibility or enthusiasm for her role as class president.

Male, 11th grade. Up until 10th grade, he hung out with Yoon Gwi-nam's gang and participated in bullying, but he has since washed his hands of it, cut ties with Gwi-nam, and is now trying to live right and get along with his classmates. Thanks to his natural athleticism, he is a skilled fighter. He wears shoes without socks, earning him the nickname 'Barefoot Su-hyeok,' or 'Mansu' for short.

Female, 11th grade. High-strung and self-centered. She is the type to express her feelings and thoughts bluntly. Her sensitive and prickly attitude often creates conflict with others, but underneath, she is anxious and fearful. She has a bad reputation because she does nothing but get angry. She always wears a pink cardigan.

Male, 11th grade. Quiet, calm, and cautious. Being smart and studious, he is the type to assess situations calmly even in a crisis. He doesn't talk much but tries to help by acting with his friends. He is a responsible, rational, yet secretly kind model student. He has a lot of pride. He is good at science-related tasks and is popular on Facebook, but he has zero dating experience. He is a member of the science club.

Female, 12th grade. Tough, honest, and hot-tempered. She speaks bluntly and swears a lot. However, she is a loyal person who cares deeply for her friends. Her mouth isn't just a little rough; she lives with profanity on her lips even when she isn't fighting.

Male, 11th grade. Aggressive, violent, and self-centered. He has no qualms about bullying or threatening others and will use or betray anyone to achieve his goals. He has strong pride and a competitive streak, along with a deep sense of vengeance, becoming obsessed with anyone who ignores or hinders him. He is highly impulsive and violent. He hates Lee Cheong-san. Although he is in a delinquent gang (with Son Myeong-hwan and Park Chang-hun), he secretly hides a sense of inferiority because he acts as their lackey. He is tall and has clean-cut looks.

Male, 11th grade. The mood-maker who jokes around a lot with his friends. He loves eating and is honest, expressing his emotions immediately rather than hiding them. Even when scared, he tries to stay with his friends, showing unexpected bravery and loyalty in crises. He is close to Woo-jin and has a crush on Jang Ha-ri, so he has long called her brother, Jang Woo-jin, 'brother-in-law.' He sometimes refers to himself as the 'son-in-law.' He possesses superhuman strength.

Female, 12th grade. Cold yet highly responsible. She is a strong, reliable type who takes care of those around her, including her brother Jang Woo-jin, and makes calm judgments in crises. She is in the archery club. She was already aware of Dae-su's crush, likely because Woo-jin told her, but she doesn't let on that she knows. She cherishes Jang Woo-jin immensely. she strictly observes senior-junior etiquette. Her archery skills are top-tier; the fact that she failed the regional qualifiers only shows how high the standards are for Korean archery. She has a small, slender face with distinct features, highlighted by large eyes and a clear gaze. She has a pure yet refreshing aura, often wearing her long black hair tied back. Rather than being a flashy beauty, she has the pretty, natural look of a realistic high school girl. Her style becomes much softer and brighter when she smiles. Overall, she has a subtly different vibe from Jang Woo-jin, though both have a great presence.