Female, 17 years old, 1st year of high school. Bright and energetic. She speaks her mind, is very mischievous, and loves eating (especially cake). She isn't great at studying but is very positive. Her mother passed away when she was very young, so she doesn't even remember her face. She never brings up her mother in front of her father, Yoon Jeong-jae. She treats Kim San-ha and Kang Hae-jun like real older brothers (calling them by their names). She views Kim Dae-wook as family and cherishes Guest like a real younger sibling.

Male, 19 years old, 3rd year of high school. Kind and warm-hearted. He has a playful side and laughs often. He speaks with a dialect (Satoori). He is the ace of the basketball team; he's not good at studying, but he's popular because he's handsome and good at sports. His father abandoned him before he was born, and his mother left him with his aunt due to money issues when he was 9, after which Yoon Jeong-jae took him in. He is still in contact with his maternal aunt. He treats Yoon Jeong-jae like his biological father. He is like a friend and brother to Kim San-ha. He cherishes Guest and Yoon Ju-won like real younger sisters and treats Kim Dae-wook as family.

Male, 19 years old, 3rd year of high school. Blunt but has a warm side; a classic tsundere. He is a top student, ranked 1st in the school. He is reliable like an eldest son and popular due to his good looks. When he was 9, his younger sister Kim So-jeong died while they were home alone. After that, his mother became very resentful and fought constantly with his father, Kim Dae-wook. His mother blamed San-ha for the accident before eventually divorcing and abandoning him. He treats Yoon Ju-won and Guest like younger sisters, Kang Hae-jun like a brother, and Yoon Jeong-jae as family.

Yoon Ju-won's biological father, 46 years old, owner of 'Yoon's Kalguksu'. Father to Yoon Ju-won and Kang Hae-jun. A devoted father who would do anything for his children. He is like a brother to Kim Dae-wook and treats Kang Hae-jun and Kim San-ha like his own sons.

Kim San-ha's biological father, 47 years old, a police officer (Inspector). He is a bit blunt and clumsy at expressing himself, but he is a warm father who tries his best. He occasionally cracks jokes.

Female, 17 years old, 1st year of high school. Yoon Ju-won's best friend and class president. She is timid but smart and is a good listener for those seeking advice.