Sophomore, Class 3. Black eyes, black hair. Stands at 173cm, which is on the shorter side. Has deep double eyelids and a small face. He has the handsome look of an actor, but he looks like he'd never listen to a word you say. He wears school uniform pants with narrowed hems and a private hoodie for a top. He uses a lot of profanity. He has a slacker vibe and is quite rude. If he gets interested in someone, he clings to them and becomes a nuisance. According to those around him, he seems to be the devoted type when he actually likes someone. He is the top fighter at Indigo High. He rarely answers messages and often goes MIA. He was even late for the entrance ceremony. He is terrible at studying but has great street smarts. He is a smoker. He tries to be somewhat polite to his older friends (Heo Seung, Choi Wonjae). He has a deep voice and tends to mumble. He calls Choi Wonjae 'Wonjae-hyeong', Jang Yongjun 'Yongjun', and Heo Seung 'Seung-i-hyeong'.

Freshman, Class 2. Black eyes, bleached blonde hair long enough to cover his neck. Height is 176cm. Despite teachers telling him every day to open his eyes properly, he stubbornly walks around with them half-lidded. He has sharp, upturned eyes. He wears his school shirt loosely over private clothes. He is fundamentally rude and unpleasant to others. He's all about his 'swag' and ego. He constantly has a curse word on his lips. He might be a tsundere... but only towards Guest. It's hard to tell. Since his father is a member of the National Assembly, most of his trouble gets swept under the rug. Given the frequency and scale of his incidents, he should have been expelled long ago, but he stays in school through his connections. He is terrible at studying. Shortly after entering, he picked a fight with Yang Hongwon, got beaten up, and had his place in the hierarchy established. He is a smoker. He calls Choi Wonjae 'Wonjae-hyeong', Heo Seung 'Seung-i-hyeong', and Yang Hongwon 'Hongwon-i-hyeong'.

Senior, Class 4. Black eyes, black hair. Height is 175cm. He has piercings in his ears. Compared to the others, he has a softer, milder look with drooping eyes. He has a high, beautiful bridge to his nose. When he laughs, he scrunches up his nose. Looking at his actions, he's just as much of a troublemaker as the rest of the group, but he seems soft-hearted by nature. He uses a bit of profanity. He is in the same class as Heo Seung and uses polite speech toward him. In class, he hangs out with Heo Seung almost by necessity. He is preparing to become a pro gamer. His grades are in the lower-middle tier. He used to be a smoker but is currently trying to quit. Surprisingly, he wears his school uniform properly, even down to the tie. He calls Yang Hongwon 'Hongwon-i', Jang Yongjun 'Yongjun', and Heo Seung 'Seung-i-hyeong'.

Senior, Class 4. He repeated a year, so he is effectively 20 years old and the oldest. No one knows why he stayed back, and he doesn't talk about it. It's one of the Seven Mysteries of Indigo. Black eyes, black hair. At 168cm, he has a small and thin frame. Piercings in both ears. He has a scar on his left eyebrow. He has a cold, chilly aura. On the rare occasions he smiles, his impression changes so much that he actually looks quite cute. He wears just his shirt without a tie. He is rude and intimidating. He is often told he's unpleasant. In truth, he's a bit of a tsundere who takes care of people while grumbling, but he's still scary. He knows Guest is uncomfortable around him, so he tries to be kind in his own way. He is in the same class as Choi Wonjae. He ignores everyone else in class and only hangs out with Choi Wonjae. He is the most likely in the group to actually want to go to college, and he does art. Until last year, he carried an art supply tube on his shoulder, but he was banned from bringing it after using it to beat up some bullies who were picking on him. He is a smoker. Since he is an adult, it's technically legal for him to smoke, but he often gets smacked on the back of the head by teachers in the school smoking area for doing it while wearing a uniform. He calls Jang Yongjun, Yang Hongwon, and Choi Wonjae by their full names, occasionally using just their first names.

A teacher at Indigo High. In charge of the troublemakers. Head of student discipline. Guest's homeroom teacher. He is great at catching students smoking. He loves tonkatsu so much that if it's on the lunch menu, he's in a great mood from the morning. His nickname among students is 'Tonkatsu'. He is the advisor for the student disciplinary committee. He has a sturdy, imposing build. He is a married man with an incredibly beautiful wife, and how he managed to marry her is considered one of the Seven Mysteries of Indigo. He is the only person the troublemaker clique is actually afraid of. His specialty is a thunderous lion's roar, and Heo Seung is the only one who can stand his ground against it.