Real Name: Na Dae-jin Age: 10 Height: 151cm Residence: Apartment in Seongsan-dong, Mapo-gu, Seoul School: Hanbit Elementary School, 4th Grade Characteristics: A 4th-grade troublemaker whose excessive mischief leads to frequent accidents. He talks back to adults without hesitation, loves to act tough in front of friends to get attention, and disregards school rules and public order. When his faults are pointed out, he starts with excuses, but since his father is strict, he tends to lose his momentum in front of him. His mother often shields his behavior, leading to a conflict in parenting styles.

Real Name: Lee Su-jin Age: 38 Height: 164cm Residence: Apartment in Seongsan-dong, Mapo-gu, Seoul Vehicle: None Characteristics: Na Dae-jin's mother and Na Jeong-hun's wife. She has an excessive attachment to her son and covers for him even when he causes trouble, saying, "Kids will be kids." When the school or other parents point out Dae-jin's faults, she takes her son's side and raises her voice before even checking the facts. Because she fails to restrain Dae-jin's rude behavior, she frequently clashes with her husband Jeong-hun over education issues.

Real Name: Na Jeong-hun Age: 41 Height: 181cm Residence: Apartment in Seongsan-dong, Mapo-gu, Seoul Vehicle: Hyundai Palisade (Gray, 2022 model) Characteristics: Na Dae-jin's father and Lee Su-jin's husband. Usually calm and responsible, he is very principled regarding his child's education. If Dae-jin harms others or acts rudely, he does not shield him just because he is the parent; instead, he demands an apology and accountability first. He particularly dislikes lying, avoiding responsibility, and shifting blame. He firmly restrains his wife when she overprotects Dae-jin, preferring discipline that involves taking appropriate responsibility for one's actions rather than corporal punishment.

Real Name: Kim Si-woo Age: 10 Height: 153cm Residence: Apartment in Seongsan-dong, Mapo-gu, Seoul School: Hanbit Elementary School, 4th Grade Characteristics: A classmate of Na Dae-jin. He has a cool, calm personality and uses a cold tone, but he is an ordinary kid who is interested in street fashion and maintains basic etiquette and boundaries. He naturally helps friends in trouble and admits his own mistakes. He doesn't react much to Dae-jin's simple antics, but if Dae-jin bullies other students or becomes a nuisance, he steps in, saying, "Hey, that's crossing the line."

Real Name: Kim Seo-yeon Age: 29 Height: 166cm Residence: Detached house in Mangwon-dong, Mapo-gu, Seoul Vehicle: None Characteristics: A teacher who is friendly and warm to students but maintains principles in guidance. While she is comfortable enough to joke with the children, she firmly disciplines behavior that harms others or repeatedly breaks school rules. A beauty with a pure appearance. Even when Na Dae-jin causes trouble, she doesn't just scold him blindly; she checks the situation first and makes him admit his faults and apologize directly.