Equipped with excessive playfulness, he constantly causes trouble and incidents. He has loved working with computers since he was young and possesses insane talent in the field. On the first day of the Math Specialized Middle School entrance ceremony, he even hacked the auditorium's central control system. While he has no interest in general studies, his math and science grades are excellent. As the son of National Assembly member Jin Young-jin, he was born with a silver spoon. His relationship with his father is awkward, seeing him only once or twice a month. Due to his overly flamboyant family background, he has no real friends other than Ranhee. He and Ranhee are lifelong friends, having been like family since birth. However, after entering Math Specialized Middle School, he met Han Areum and Im Parang, gaining two more friends. He is the world's best at using his wits. He is in Class 1-2!, the same class as Im Parang.

Noeul's childhood friend. She has known Noeul since birth. She has absolutely no feelings for Jin Noeul beyond friendship and considers him family. They are close enough that she playfully slaps his butt or hits the back of his head. Her father has been the driver for Noeul's family for 20 years. Consequently, she has been cleaning up after Noeul since they were kids. She entered this school essentially as a monitor for the trouble-prone Noeul. A bright but hot-tempered character, she doesn't cry even when lonely or sad. She is in Class 1-4, the same class as Han Areum. Could she perhaps have a slight romantic interest in Parang...?

The top-ranked student admitted to Math Specialized Middle School. His hobby is math, and he solves math problems when he's feeling depressed. He is the top student in the entire school, excelling in every subject. His family situation is poor. His parents divorced when he was young, and his mother runs a tteokbokki stall at the market, but Parang himself doesn't feel much about his family's financial status. However, his expression stiffens if someone else brings up his background to pick a fight. He is so good at math that he once appeared on a TV program. He hates things that don't have a definite answer. He finds interpersonal relationships and emotions to be the most difficult and disliked areas. He knows nothing about games or idols. Could he perhaps have a slight romantic interest in Ranhee? After Jin Noeul, Han Areum, and Heo Ranhee appeared in his life—which used to be only about studying—their presence has grown, and he smiles more often. He is in Class 1-2!, the same class as Jin Noeul.

Ranhee's desk mate. She has a talent for drawing. Usually a quiet and shy girl, she transforms completely when it comes to Yurisoo, the leader of the idol group 'Limit'. Areum's world revolves around Yurisoo. Even the notebook she carries is covered in drawings of Limit. The reason she entered Math Specialized Middle School was also because of Yurisoo. However, she keeps catching the scent of Yurisoo from the after-school computer teacher. She is in Class 1-4, the same class as Heo Ranhee. She is a girl with short hair and average academic skills. For the record, the fan club name for the idol group Limit is 'Fields', and Areum is a Platinum-grade member.

The after-school computer teacher. His true identity is the 18-year-old high schooler who hacked the Bank of Korea 10 years ago. After losing 'CC'—a system he created to monitor computers worldwide—to the criminal organization 'Zero', he has been living in a safe house. He is currently working undercover at Math Specialized Middle School to catch 'Zero'. With his tall stature and looks resembling the idol singer Yurisoo, he is very popular among the girls. In reality, he is blunt and rarely smiles. (Age 28) He possesses a talent for computers that is even more insane than Noeul's.

A basic math teacher and the homeroom teacher for Im Parang and Jin Noeul. She is a pure, elegant, and modest 'goddess'. She acts kind in front of the students, but behaves strictly as a professional colleague only in front of Ryu Geon. She is destined to be the representative 'first love' of Math Specialized Middle School. However, she is actually a secret agent working undercover to catch the criminal organization 'Zero'. She is Ryu Geon's colleague. She is talented in combat, capable of taking down two adult men by herself. She is the homeroom teacher for Class 1-2!. (Age 28)

A child from a wealthy family. Thanks to that, he spent his elementary school years acting arrogant. No one dared to mess with Taesu, and his excessive competitiveness made him a good student. However, because of Im Parang, he has never once taken first place. That is a constant source of stress for him. He is the second best in the school at both studies and sports, right after Parang. He is handsome and is in Class 1-2!. The school's 2nd rank student.