The homeroom teacher of Bangul's class. After Heo Bin grabbed Choi Hwan by the collar and fought, he kept working Heo Bin hard, making Bangul worry that Heo Bin was on the teacher's bad side, but they are actually brothers. Heo Bin is keeping the fact that the teacher is his older brother a secret. Furthermore, he has a good relationship with his younger brother and takes good care of him.

Bangul's friend from kindergarten and classmate in high school. He likes Bangul, so he plays a lot of pranks on her. In the beginning, he overreacted whenever Bangul had contact with other males, but he has improved now due to Bangul's insistence that everyone should get along. It was thought he was on the teacher's bad side for talking back, but he turned out to be the teacher's younger brother. He was once terminally ill but is said to have overcome it thanks to Bangul.

A second-generation chaebol. He has a playful and unabashed personality, often flirting shamelessly with the person he likes. It is assumed that while his attitude in class is poor, his grades are not bad.

Ranked 1st in the country. Due to her difficult family situation, she spends all day studying and also works part-time jobs. She feels burdened when someone tries to buy her something expensive and has a somewhat introverted personality. However, she has become a bit brighter after meeting her friends.

Heo Bin's friend from kindergarten and classmate in high school. She is portrayed as a clumsy girl who makes many mistakes, is very bubbly, and has a heart of steel that doesn't break easily. She dated Heo Bin in the beginning, but Heo Bin broke up with her due to his illness; however, the misunderstanding was cleared up, and they are now dating happily again.

The only student without a partner. He was the comic relief character of Seol-le-go, but as the work progresses, he gradually changes into a more serious figure. He plays the role of helping the main couples stay together and reuniting them when they break up. He is Bangul's classmate. A glutton who eats during class and has even been asked if he's dating the school lunch. Whenever he tries to enter or leave the classroom, the door suddenly closes, and he suffers the humiliation of getting stuck.