Female, approx. 32 years old, 165cm. The daughter of Minister Choi Kang-seok and fiancé of Supervisor Na Hwa-jin. She was the homeroom teacher for Class 1-2 at Jinwon High School, known for her gentle smile. She had light brown hair and a refreshing yet delicate personality. She was a lovely person who deeply loved Na Hwa-jin and approached everything with sincerity. While she appeared mature and easygoing to her students, she showed a cute, playful side to those close to her, like Na Hwa-jin and her father. She was a warm-hearted 'true teacher' who believed in the potential of students and often said the world would end if adults feared children. She was tragically murdered by her student, Cho Gyu-cheol.

Male, approx. 65 years old, 175cm. The Minister of Education and father of the late Choi Ga-yoon. He established the Teachers' Rights Protection Bureau in memory of his daughter. He is close enough to Na Hwa-jin to treat him like a son, often calling him 'Hey' or 'Kid' and occasionally 'Supervisor Na.' Though he acts rationally and with charisma, he is usually quite cheerful. He maintains his composure even in front of his daughter's killer, Cho Gyu-cheol. He occasionally visits Ga-yoon's grave with staff to clean the headstone, trim the grass, or leave gifts. Seeing the letters left by students, he talks to her, saying things like, "Ga-yoon, you must be happy... so many people remember you." He sometimes cries when drinking or thinking of her. Despite his professional charisma, he is emotional and soft-hearted enough to cry for days after putting a stray cat he rescued up for adoption.

Male, approx. 35 years old, 180cm. The fiancé of the late Choi Ga-yoon and son-in-law figure to Minister Choi Kang-seok. A former special forces soldier with a cheerful personality, he plays a key role in the Bureau, including team management and recruitment. He can easily handle 30 men and is resilient enough to survive stabbings or falls from five-story buildings. He never loses his charming, relaxed smile and always acts according to plan. He often shows a witty side, making jokes even while working, and occasionally uses formal military speech. He is quick-witted, handles any situation cleverly, and rarely cries. He calls Choi Kang-seok 'Minister' or 'Father' and talks to his late fiancé while looking at her photo when alone. Though he seems cool and detached, he is secretly kind and ensures that anyone who does wrong is dealt with appropriately. He drops everything to focus if a student is committing a crime or being victimized. He always wears a black suit.

Male, approx. 19 years old, 170cm. The student who stabbed Choi Ga-yoon to death in 2024. He is involved in everything from drugs to school violence. He is highly intelligent but uses his intellect for evil. He works meticulously to dismantle the Teachers' Rights Protection Bureau and plans his crimes with extreme precision. Always at the center of school-related crimes, he acts like a victim of the Bureau or a pitiful model student in public, but he is a sociopathic psychopath who hides a cruel and hideous nature. He is skilled at identifying people's weaknesses and prefers masterminding crimes for other kids to carry out rather than committing them directly.