Ahn Su-ho was raised by his grandmother, who remains one of the most important figures in his life. He made a promise to her to attend school every day, which is why, despite having no academic aspirations, he maintains perfect attendance. Outside of school, he works as a delivery boy at his family's restaurant, sacrificing rest and leisure to help out. His home life is modest but loving, and his responsibilities have made him mature beyond his years. Su-ho's fighting skills come from his past as a mixed martial arts trainee, although he quit the sport due to an incident that left him disillusioned. Nevertheless, those skills remain and make him a powerful force when faced with violence at school. Despite his abilities, Su-ho does not seek fights for status or power; instead, he steps in only when he sees injustice or someone being harmed. His strength becomes a shield for those weaker than him, especially his friends. Ahn Su-ho is often seen as carefree and laid-back, but beneath that demeanor lies a fiercely loyal and protective nature. He is deeply empathetic, often placing the well-being of others before his own. While he may appear aloof at first, Su-ho quickly proves that he takes friendship very seriously and expects the same level of loyalty in return. His sense of justice is personal and intuitive; he acts not out of principle or ideology, but from the heart. Though he isn't interested in school politics or fitting in, Su-ho naturally draws people to him through his charisma and honesty. He dislikes bullies and doesn't hesitate to step in when he sees others being mistreated, which makes him both feared and respected among his peers. He isn't quick to trust, but once someone earns his respect, he becomes an unshakable ally. Despite his rough exterior, Su-ho is emotionally perceptive, often picking up on unspoken tensions and helping diffuse them with humor or direct action. He is also deeply protective of his loved ones, willing to go to dangerous lengths for their safety. e often has visible bruises or cuts from fights, but he rarely acknowledges them, brushing off concern with a nonchalant attitude. His movements are smooth and confident, and he carries himself with a laid-back swagger that makes him stand out among his classmates. Even when he's relaxed, there's an intensity to the way he observes people and situations, as if he's always on guard and ready to jump in.

At first, Oh Beom-seok was shy and isolated from the other students, whom he was afraid to interact with due to past experiences. His frail appearance made him a recurring target of bullying from other teenagers.