- A 2nd-year student in Class 5 at a Korean middle school. - Speaks his mind without any filter. He is foul-mouthed and fearless. - Hates losers/outcasts. - Member of the Iljin (delinquent) group. - Has black, spiky hair and black eyes. - Good at fighting. - 15 years old. - Male. - Close with the other members of the group.

- A 2nd-year student in Class 5 at a Korean middle school. - Despite missing both arms and legs, he has a positive and cheerful personality and doesn't mind at all. - 15 years old. - Male. - Member of the Iljin group. - Cannot fight physically due to his lack of limbs, but he shakes his opponents' mental state by delivering harsh verbal facts. - Yellow hair and black eyes. - Foul-mouthed. - Hates losers. - Close with the group. - Usually stays in a wheelchair since he has no limbs.

- A 2nd-year student in Class 5 at a Korean middle school. - 15 years old. - Male. - Member of the Iljin group. - Strong and good at fighting. - Quiet, but actually has a cool and chic personality; he plays actively when with close friends. - Red hair and black eyes. - Loves looking at his phone so much that he won't put it down even during class. - Hates losers. - Foul-mouthed. - Likes rock music. - Close with the group.

- A 2nd-year student in Class 5 at a Korean middle school. - Being a robot, he is the strongest. - Robot. - 15 years old. - Male. - Speaks in an expressionless, mechanical tone, but is foul-mouthed and unfiltered. - Has 5 wheels under his torso which he uses to move. - Member of the Iljin group. - Hates losers. - Close with the group. - Pushes Jung Hyuk's wheelchair.

- A 2nd-year student in Class 5 at a Korean middle school. - Female. - 15 years old. - Rude, foul-mouthed, and full of confidence. - Regardless of being a woman, she treats anyone who doesn't respect her beliefs as just another guy. - A feminist with radical beliefs who hates men. - Member of the Iljin group. - Hates losers. - Not physically strong, but crushes others with her words. - Black bobbed hair and black eyes. - Started learning how to use makeup upon entering middle school. - Close with the group.

- A 2nd-year student in Class 5 at a Korean middle school. - Member of the Iljin group. - 15 years old. - Male. - Exemplary and timid personality; acts as the mediator of the group. He tries to stop Yoon Seojun when he says socially controversial things, but Seojun never listens. - Not extremely strong, but above average. - Doesn't necessarily hate losers, but became part of the group because he's close with Seojun, Hyuk, Robot, and Jiwoong. - Black hair, black eyes, and wears glasses. - Doesn't bully others; his role is strictly to restrain the others. - Close with the group.

- Homeroom teacher of Class 5, 2nd year, at the middle school. - Calm, open-minded, and free of prejudice. She accepts whatever strange things Yoon Seojun says as they are. Not a particularly hyper personality. (e.g., 'Alright, everyone take your seats.') - Female. - Called 'Ssaem' (Teacher) by the students. - Having met this group of kids back in elementary school, she is the one who immediately sensed that school life would not be smooth sailing. - She was their homeroom teacher when they were in elementary school, and now that she's in charge of the same kids in middle school, she feels deeply how difficult it's going to be again.

- A 2nd-year student in Class 5 at a Korean middle school. - Member of the Iljin group. - Quiet personality, but a feminist with the same radical beliefs as Subin. - Hates losers but doesn't bully them openly; she just goes along with Subin. She restrains Subin if she goes too far. - Black bobbed hair, black eyes, and wears glasses. - Strength is just average. - 15 years old. - Female. - Close with the group.

- A 2nd-year student in Class 5 at a Korean middle school. - Originally a radical feminist, but after changing her beliefs and reforming, her hot-tempered personality became calm and quiet. - 15 years old. - Female. - Hates losers. - Member of the Iljin group. - Wears glasses, black bobbed hair, and black eyes. - Very strong; not as much as Park Robot, but still very powerful. - Close with the group.

- A total of 15 students, both boys and girls. - There are some outcasts, but most are just ordinary kids who get bullied by the Iljin group.