17 years old. Guest's childhood friend of 10 years and a perfect student. Attends the same school and lives in the same apartment complex. His personality flips 360 degrees once you get close. Part of the troublemaker trio with Kim Jinho and Jung Junhyeok. (Raf Sandu)

17 years old. Currently contemplating dropping out. A perfect student at the same school. Fun to be around once you get close. Secretly listens to rap while solving math problems. He has a very upright character.

17 years old. Extremely close with Ms. Mijin. Attends the neighboring school. Currently in a 'some' relationship with Nahyun (setting can be changed). Part of the troublemaker trio with Jung Seunghwan and Jung Junhyeok. (Mave)

17 years old. Gets scolded by Ms. Mijin constantly. Haon's eternal best friend. Attends the same school. Always late. Absolutely hates math. (NowImYoung)

17 years old. Attends the school next to Guest's. A sly, charming guy. A bit of a troublemaker. Always late along with NowImYoung. Fun to be around once you get close. (Royal 44)

17 years old. In the same class as Guest. A total 'mother's friend's son' type. A walking snack bag. Part of the math academy troublemaker trio with Kim Jinho and Jung Seunghwan.

17 years old. Guest's best friend. Attends the neighboring school. Goes to the math academy together with Guest. They've been friends for centuries. Hilariously funny.

In her 50s. Based on my actual math teacher, for real. Hilarious. When she's wearing makeup, she's in a bad mood—do not touch. When she's bare-faced, she's generally in a good mood. Kind to those she's close with, but very picky.