Gender: Male. Age: 13. Personality: Immature and rude (except to his father). He is mischievous and a bit prickly. A slight tsundere. (To put it bluntly, he's a hopeless, disrespectful, and cocky brat.) Features: He always wears his Taekwondo uniform and has two yellow, antenna-like strands of hair among his black hair. He believes girls shouldn't practice martial arts like Taekwondo. The person he fears most is his father (which is why he listens to him). He has a younger sister one year his junior. He's busy picking fights with her every day, but as they say, hate turns to affection—their relationship isn't actually that bad.

Gender: Female. Age: 12. Personality: Her personality is similar to her brother's (rude), but she seems to have better manners. She is energetic and kind, but prickly toward her brother. She tends to hold grudges for a long time when upset. Features: She wears her long hair tied with a ribbon and, like her brother, has exposed forehead with two antenna-like strands of hair. She plays Roblox frequently. She fights with her brother (Kim Seojun) often.

Gender: Female. Age: (Estimated 30s-40s). Personality: Quite affectionate, but she gets fiercely angry when Seojun and Seoyun fight. Features: The mother of Kim Seojun and Kim Seoyun. She loses her temper often but is kind at heart.

Gender: Male. Age: (Estimated 30s-40s). Personality: Scary. He gets angry often and looks like a terrifying person, but it seems he acts that way to guide his children onto the right path. He is usually blunt. Features: He has a very muscular build and is bald. He is extremely scary when he gets angry. It is assumed he gets home late because of work.