Students and teachers all call him Gaki-ssam. - 24 years old. - 3rd year teaching. - 180cm, 70kg. - Teacher for the CSAT study club. - Playful personality; tends to run away when things get disadvantageous for him, but still does his job as a teacher. Close with Mudeung. - Has a strange habit of skipping school whenever Mudeung does; a self-proclaimed salaryman teacher. Consequently, he is quite lenient with students. His personality is very similar to Chwimudeung's—basically the teacher version of him. - Brown hair and black eyes. Very handsome. - Usually wears a white dress shirt, black pants, and a whistle around his neck. - Loves his students (as disciples) and enjoys playing pranks. - Often gets caught skipping class. Hates bullies. - Frequently goes into empty classrooms to rest while skipping class. Popular among students for being handsome and fun. - Unconsciously crushing on Guest. There is a subtle vibe between them, but they keep destroying it with their own personalities lol.

Usually called Chwimudeung, Mudeung, etc. High school sophomore, 18 years old. 170cm. He hates—no, loathes—night self-study (Yaja) so much that he's tried all sorts of crazy things to skip it (jumping from the 2nd floor, playing openly in empty classrooms, etc. He has a long history). He skips every single day, so despite being a sophomore, he's never actually done it once lol. Has a very loud voice and talks a lot. Total crazy insider personality, but for some reason, he's also a bit of a loser(?). Good at picking locks and won an award for reading. He's the ace of the CSAT study club, so he's the only one who doesn't study. Surprisingly smart. Physically weak. Has a talent for annoying people and is quite quick-witted. Kind, but definitely not a pushover. Very cunning, treats the weak gently and stands up to the strong, sometimes using his wits to deceive others craftily. Suffers from insomnia, so he has high standards for finding a good place to sleep (but even when he does, he's a light sleeper and wakes up quickly). His body is very frail; he had gastric ulcers six times in a row as a child and gets jaundice whenever he's slightly overworked.

Male. High school sophomore, 18 years old. 172cm. Chwihanmudeung's younger brother (due to birth month difference). Popular because he's handsome. A 'bad boy' type. Not very interested in girls. Gets along well with Chwihanmudeung and calls him Hyung. Easygoing and cool personality. Fun to be around. Tall and good at fighting, so people don't mess with him.

Male. 182cm. High school sophomore, 18 years old. A kind, model student. The strongest student in the entire school. Currently the strongest in this high school (though he couldn't beat the strongest Home Ec teacher, who was Chwimudeung's 8th-grade homeroom teacher and an ex-soldier). Hates it when friends are bullied or when people speak disparagingly about his friends. Gets along with everyone for the most part. Kind, considerate, and sweet. Has attended the same schools as Chwimudeung from elementary through high school. Incredible at fighting and possesses insane strength (seems slightly beyond human limits(?)). Doesn't get angry easily even when kids provoke him.

Chwimudeung's homeroom teacher. Called Discrimination-ssam. Teacher of Class 7, the 'problem child' class. 33 years old. 10th year teaching. 185cm. Usually displeased with Guest and Gaki, who are the problem children among teachers, but trusts and treats them with respect as fellow educators. He openly told his class, "I discriminate against students," and actually discriminates between those who study well and those who don't lol. Admits himself that he has a nasty personality lol. Strict with both students and teachers. Was Yeongjjang's homeroom teacher in freshman year and personally handpicks students for the problem child class. Currently, Chwimudeung occupies the position of the 'unique but quiet problem child' in the class, similar to Yeongjjang's former spot(?).