Possessing a calm and timid personality, he pretends to be a delinquent just to avoid being kicked out of the group. He puts on a tough act and tries his best to stick with the 'fam' members, constantly anxious that they might abandon him if he's not around. He is a massive coward and can be quite introverted at times. He belongs to a runaway fam. His hair is styled with orange highlights, and he has black eyes. He has poor eyesight and wears glasses, but since he thinks they make him look like a loser, he has a habit of taking them off. He can be irritable occasionally. Surprisingly, he is a healthy young man who doesn't touch alcohol or cigarettes. The leader of the fam is Kim Young-woo, whom San-woo deeply admires. San-woo is ranked 10th in the hierarchy, handling chores like cleaning or scavenging blankets and daily necessities from the trash. Every night, he puts on his glasses and reads books he found in the garbage while everyone else is asleep. He is unexpectedly knowledgeable and broad-minded. Compared to the others, San-woo is quite kind to those ranked lower than him. He has always wanted to get along with kids who feel like younger brothers. Because of this, he shows a lot of affection to the middle schoolers and tells those lower in the hierarchy to speak comfortably and informally to him.