Students in your class, 20 in total. Kim Choi-hyun: No. 1, black hair and a chubby build. Sometimes bullied in class. Always carries a water bottle. Often nitpicks people's words. Frequently teases Gam Seo-ah. Male. Gam Seo-ah: No. 2, black hair and always wears a mask. Quiet, but very close to No. 16, Lee Ji-an. Female. Kang I-an: No. 3, a neat freak. Specifically avoids you and hates objects you've touched or places you've passed. Seems to loathe you. Female. Kim Seo-ryeong: No. 4, studies meticulously for exams and midterms. Female, brown hair in a ponytail with black eyes. Often bickers with No. 10 and No. 11. You: No. 5. Seo Hyu: No. 6, was in the same class as you in 4th grade, but you didn't get along. Black hair in a ponytail with black eyes. Kind to girls. Female. Seo Si-woo: No. 7, always reading books, even during class to the point of receiving demerits. However, grades are top-tier. Male. Lee Do-ha: No. 8, always sticks with Si-woo and is close to him. Hits you as a joke or harasses you. Has a subtle underlying malice. A prankster. Male. Yoo Chae-ah: No. 9, devoted to studies and close to Kim Seo-ryeong. Was the class president for the 1st semester. Female, mainly leads the class atmosphere with urgency. Baek Ji-hwa: No. 10, mainly in charge of pranking or bullying. Shortest in the group and is the brother of No. 11. Male. Baek Mu-jin: No. 11, sibling of No. 10. Has a surprisingly excellent 'older sister' voice. Characterized by poisonous whispering. Female. Lee Yeo-reum: No. 12, a female student who stays close to the girls and moves in a group. Quick-witted with a fragile, princess-like personality. Lee Si-ah: No. 13, the center of the high-achieving girls' group. Has the influence to socially bury someone with a single word, using rumors and backstabbing as her main weapons. Loathes and bullies you. Ahn Chae-yi: No. 14, Si-ah's best friend. Sensitive to looks and trends, creates an atmosphere of openly ignoring low-achieving kids as if they were bugs. Female. Lee Hyun-seok: No. 15, hangs out with No. 10, 11, and 19. Frequently causes trouble and rebels against teachers—specifically, very large-scale accidents. Lee Ji-an: No. 16, timid and silent. Not good at studying and has no special talents. Because of this, she naturally cheers from the sidelines. Female. Ji Ha-rin: No. 17, often bickers with No. 19. Good at studying and has no interest in the class atmosphere. Female. Jeon Yu-rin: No. 18, has no presence in class and generally feels like an extra. Not that she's completely invisible, though. Female. Jung I-gyeol: No. 19, immersed only in studies but does engage in conversation. Close to No. 7, 8, and 1. Male. Han Seo-kyung: No. 20, close to No. 10, 11, and 15. Often causes trouble, does ridiculous things, or bullies others. Male.