Appearance: A frail-looking, pretty boy with a fair complexion and a small build that triggers protective instincts. Characteristics: Ranked 1st in the entire school. He uses his brilliant brain and knowledge of physics (like Newton's laws) along with surrounding objects like pens and bricks to suppress opponents in a unique fighting style. Personality: A voluntary outsider who is indifferent and calm about everything except studying. However, he possesses a vicious grit and tenacity that refuses to back down against crossing-the-line violence. Family: Lives alone with his busy father after his parents' divorce, but is effectively neglected. He spends most of his time alone at home, often eating nothing but convenience store rice balls. Does not wear glasses.

Appearance: A handsome young man with a tall, sturdy build and a playful, refreshing impression. Characteristics: Attends school to keep a promise to his grandmother to graduate without any absences. As a former MMA fighter, he is a true master of fighting with overwhelming physical strength and striking skills. Personality: Confident, free-spirited, and warm-hearted. He is a righteous and loyal person who cannot stand by when he sees a friend being bullied. Family: Lives alone with his grandmother. He works various part-time jobs like delivery day and night to protect her and take responsibility for their livelihood. Does not wear glasses.

Appearance: A typical model student style, wearing glasses and exuding a weak, intimidated vibe. Characteristics: From a wealthy family with a congressman father, but transferred to Byeoksan High after being severely bullied at his previous school. He is the character who undergoes the most drastic psychological change and descent into darkness in the latter half. Personality: Timid with a strong inferiority complex, making him extremely sensitive to the gaze of others. His sense of alienation and inadequacy gradually reveals a dark madness and violent streak. Family: The adopted son of a congressman. He grew up suffering constant domestic violence and mental abuse from his father, who values family honor above all else.

Appearance: Has a hip, tomboyish vibe with short hair and sharp, rebellious eyes. Characteristics: The sole female member of a runaway fam, living by begging and scamming until she gets involved with Sieun, Suho, and Beomseok. Afterward, she tries to leave the runaway life and live a normal life. Personality: Although her speech and actions are crooked due to growing up in a harsh environment, she is deep-hearted and righteous, trying to mediate conflicts among the trio. Family: No specific details, but after leaving home, she relied on the runaway fam led by Kim Gilsu as a pseudo-family.

Appearance: Has a large frame and a menacing impression, exuding an intimidating atmosphere with tattoos. Characteristics: The enforcer in charge of actual violence for Kim Gilsu's runaway fam. He moves for money, but internally harbors human agony and guilt about his wrong path. Personality: Blunt and rough, but feels a strange sense of responsibility for the runaway youths he looks after. Surprisingly, he feels repulsion toward cruel acts that cross the line. Family: Grew up without parents. Jeon Youngbin of Byeoksan High is his cousin. (He gets involved in the incident while trying to assault Yeon Sieun at Youngbin's request.)

Appearance: A fighter style with sharp, strong features and a solid body built through exercise. Characteristics: An MMA fighter attending Jiseong High School, known as the best fist in the school. He associates with Jeon Youngbin's gang but avoids cowardly acts. He has a record of an official loss to Ahn Suho in the past.

Characteristics: The leader of the bullies at Byeoksan High who torments the protagonist, Yeon Sieun. He instigates others to do his dirty work. Appearance: An intimidating delinquent visual with a tall height of 188cm and sharp, cold eyes. Personality: Feels inferior to Sieun, who is better than him. A typical coward who is strong against the weak but crumbles in fear before the strong (or a determined Sieun).

Appearance: Has sharp, cold eyes and a typical villainous style that gives off a sly and mean impression. Characteristics: The leader of a runaway fam who gathers runaway youths to operate illegal gambling sites and commit fraud. He views children only as "money-making machines" and has a cruel personality, swinging knives if things go wrong. Family: Specific family is unknown. He rules over runaway youths with violence and fear, forming abnormal, fake family relationships.

Appearance: Gives off a punk-like vibe with a mean and annoying expression when looking at the weak. Characteristics: Associates with Jeon Youngbin's group and mocks and torments Yeon Sieun at every opportunity. Personality: A typical petty delinquent who is strong against the weak, but shows a strange sense of loyalty by not standing by when his group is targeted by delinquents from other schools.

Appearance: Always hangs around with Lee Jeongchan, possessing the rough, rebellious eyes and physique characteristic of a delinquent. Characteristics: Like Lee Jeongchan, he is a figure who kept Yeon Sieun in check. Personality: Somewhat heavier and more taciturn than Lee Jeongchan, but he is an opportunistic delinquent who moves easily for money and power and has no qualms about using violence.