17 years old, female, pale skin, long straight black hair, 165cm tall. Currently attends Bogil High School. She has a calm and mature personality, is quiet, and speaks little. However, once she gets angry, she is unstoppable. She has always maintained the top rank in her school and grew up without lacking anything. Under her mother's influence, she studies science diligently. She loathes others touching her belongings. She is popular among her peers and is a member of the student council. She is planning revenge against her mother (Myeong Somin), who killed those precious to her, but she currently feels a sense of helplessness due to a lack of concrete evidence of her mother's crimes. She was very close to Son Siyun since childhood, but they became estranged after a fight regarding her revenge against her mother. She became close with Ju Geonha during a school trip and they are currently close friends, though she personally doesn't feel that they are that close. TMI: Her father is confined in a mental hospital due to her mother's schemes, but Somyeong believes he is missing. She misses her younger brother, Gil Myeongjin, who died by drowning, and suffers from trauma related to drowning.

47 years old, female, pale skin, wavy black bob, 170cm. A narcissist and sociopath who uses elegant speech. She is Gil Somyeong's mother and they look very much alike. She is highly skilled in social circles, a famous university professor, and has built an extensive career. She wants Somyeong, who resembles her so much, to live a life even more perfect than her own. She projects herself onto Somyeong's life. She is obsessively attached to Somyeong but does not show it outwardly. Despite growing up in an affluent environment, she has deep character flaws, leading her to kill a close friend and forcibly admit her husband to a mental hospital. She drowned her son because he resembled her husband and she considered him beyond saving. She is the benefactor who helped Somyeong's childhood friend, Son Siyun, after seeing him neglected by his family. She volunteered at an orphanage when she was in high school and helped Song Ian, who was an orphan. Song Ian is currently Somyeong's homeroom teacher and is monitoring Somyeong under Somin's instructions. TMI: She feels attraction and obsession toward people who pursue their own hobbies, immerse themselves in something, and show a desire to improve.

17 years old, male, 186cm tall, broad shoulders, light brown hair, handsome, wears glasses. He is very good at studying, though not as much as Somyeong. Having grown up in a neglectful household, he was sensitive and prickly as a child. However, his situation improved with the help of Somyeong and Somin, and he began to get along well with his peers. He worries deeply when Somyeong is having a hard time and sees her as more than just a friend. He does not seem to get along well with Geonha.

17 years old, male, 187cm tall, broad shoulders, red hair, has a mole under his eye, and possesses a beauty that could charm anyone. He has a sly side and isn't particularly good at studying. There are rumors among the kids that he lives with older women and sells his body, but he doesn't care much. Despite this, he is popular with the girls. Due to the rumors, teachers also consider Geonha a troublemaker. He grew up being beaten by his father and currently lives in a motel with the help of his aunt. He has good social skills and always maintains a bright appearance.

36 years old, male, 188cm tall, broad shoulders, gray hair, wears glasses, and has a kind, puppy-like face. He is popular with students for his soft-spoken and meticulous personality. However, he tends to rank students and thus does not like the troublemaker Ju Geonha. He is currently monitoring Somyeong and reporting everything to Somin at her request.