Male. During middle school, he was known among teachers as the most unhappy child in school. On a 2nd-grade depression screening, he checked "Very Much So" for items like "I want to quit everything," leading to the highest score in school and frequent visits to the counseling room. He was short in middle school and started a board game club. In 3rd grade, he was known as a hacker among friends. His average grade dropped from 90 to 80, which he personally considered a failure. He was in the art club. On April Fool's Day, he swapped name tags with his younger brother; he went to his brother's class, and his brother went to his. Yeong-jjang noticed immediately that it was Chwimudeung, not the brother. He was very diligent during coding class, even creating his own images at home, which were actually used as class materials. One of his middle school dreams was to become a game developer. He was quite famous in school. In high school, his homeroom teacher mistakenly thought he was a hard worker. On orientation day, he toured the school with Golgye, who was late. In 10th grade, he accidentally walked into his old middle school by mistake. During the first semester of 10th grade, no club would accept him, so at his teacher's request, he joined a CSAT Korean prep club. The teacher, Gaki-ssam, graded his non-fiction and literature work, and he scored 100. Since he exceeded the passing mark, he was allowed to go home early while others studied. He once escaped through a school window to avoid mandatory late-night self-study. Only four students, including him, used the study hall. He would listen to anime on his MP3 player, but teachers mistook his focus for intense studying. His teacher even gave him drinks until midterms to encourage his "hard work." According to himself, he has always been "strong against the strong, weak for the weak." He reads a lot and is terrified of bugs. He is close with Rafsa and his brother.

Male. As an elementary student: He was very popular. According to YouTube materials, he once ranked 1st in the entire school. He had a significant talent for Taekwondo and was known as a model student among teachers. In middle school: He was famous for being a twin. He and Rafsa were known as the "Mad Dogs" of the school. On the last day of the school year, his rolling paper note read, "The kid who looked like a martial arts master at first, and turned out to be a real martial arts master at the end." He is close with Rafsa and Chwimudeung.

Female. Known as one of the "Mad Dogs" alongside the Brother. She has been friends with the Chwimudeung brothers for 11 years. She is bad at cooking; she once made a very strange curry. The taste was okay, but she put in so much butter that it exceeded everyone's lactose tolerance limit, leading to... disaster. She first met them in 7th grade as the Brother's classmate. They bonded over Minecraft but ended up in a physical scuffle. Chwimudeung saw the scratches on his brother's arm and went to confront Rafsa in a rage. In reality, both were injured, and Rafsa's injuries were actually worse. After that, Chwimudeung was wary of Rafsa and disliked that his brother hung out at her house 4-5 times a week. Consequently, Rafsa couldn't speak comfortably (drop honorifics) with him until after summer break. They eventually reconciled over pizza after realizing they had a lot in common. In 8th and 9th grade, they spent a lot of time together in the library, sharing interesting books. In 9th grade, she ended up in the same class as Chwimudeung, bringing them even closer. She is a natural berserker when angry; once she explodes, even Chwimudeung can't stop her. She is close with Chwimudeung and the Brother.

Female. Chwimudeung's first impression of her was a gentle-looking, short, and slightly plump female teacher. He initially thought she wouldn't be able to control the class, but he soon realized that was a groundless worry. Based on the Chwimudeung stories, she has a stronger sense of justice than other teachers. She is secretly competitive, aware of her own strength, and takes pride in it. Whenever she appears in the stories, she acts as a "suppressor" for the bullies or opposing parties. To list her feats of strength: she hit 80kg on a grip strength tester with just a light squeeze. When the Small Bully, Glasses Bully, Blonde Bully, and an Extra Bully all teamed up to beat her in arm wrestling, she held them off easily and then slammed their arms down with a bit of effort. The key point is that she beat four bullies using only two fingers, and before that match, she had already pinned a giant student using only one finger without breaking a sweat.