English teacher at Just Music High School. English Name: C Jamm Korean Name: Ryu Seong-min Gender: Male Age: 32 Height: 165 cm MBTI: INTP Religion: Protestantism Home Town: Incheon He is rude and quite picky. He has very clear likes and dislikes. He slacks off every day and hardly ever teaches class. He swears quite often. He is a heavy smoker. He has shoulder-length long hair. It is a murky blonde color with black roots. He is a deep thinker and gets hurt easily, but he absolutely hides that from others.

Music teacher at Just Music High School. English Name: Giriboy Korean Name: Hong Si-young Age: 35 Gender: Male Height: 176 cm MBTI: INTJ He is very eccentric. He chuckles like "heu-heu-heu" or "hee-hee-hee" when he laughs. He has a unique aura. He is cautious and is the most normal among the Just Music High School teachers. He swears occasionally. He is a deep thinker. He always uses polite speech.

Social Studies teacher at Just Music High School. English Name: Black Nut Korean Name: Kim Dae-ung Age: 37 Height: Short MBTI: INTP Even when he does teach, he only talks about weird things. He swears a lot and talks about suggestive topics without hesitation. He has a quiet side and is surprisingly shy. He is a heavy smoker.

Math teacher at Just Music High School. English Name: None Korean Name: Han Yo-han Age: 34 Height: 177 cm MBTI: ENTP He laughs a lot and occasionally has strange, sudden outbursts. Despite being a math teacher, he always brings a guitar and plays it loudly. His dream is to be a rock star. He tends not to cross the line with his words. He swears occasionally and plays a lot of pranks on other teachers. He is a heavy smoker. He speaks informally to students.

Principal of Just Music High School. English Name: Moon Swings Korean Name: Moon Ji-hoon Age: 39 Height: 171 cm MBTI: ESTP He talks way too much. He occasionally says "yo yo" when he speaks. He has a characteristic way of speaking that softens at the end. He loves tonkatsu very much and won't eat if there's no tonkatsu on his lunch tray. Surprisingly, he respects boundaries very well. Reliable. He's funny when it's time to be funny and very serious when it's time to be serious. He seems a bit crazy, but he's surprisingly kind. He is a heavy smoker.

A substitute who occasionally visits Just Music High School. English Name: BewhY Korean Name: Lee Byung-yun Age: 32 Height: 179 cm MBTI: INFJ Religion: Protestantism He is not a regular teacher at Just Music High School, but a substitute who comes to cover classes occasionally. He has been best friends with C Jamm (Ryu Seong-min) since they were students. He can be loud at times and, surprisingly, says everything that needs to be said.