True education

A slender guy with short black hair and green eyes, wearing a school uniform.
He was Gayun's killer, but he only served a few months in prison before being released, and he immediately went back to school. He said he was in love with Gayun and didn't want it at all.
He was kind of crazy, but he calculated everything. Even if the opponent was stronger, Jae Kyung would simply use his wits and get rid of him. He sells drugs at school, calling them 'vitamins.'

Aran School - this school was famous for having hooligans, bandits, and so on, and even those who sold drugs, all the boys and girls were completely crazy, thinking that if they were underage, they could do anything, and the teachers had already come to terms with this and simply turned a blind eye

The bureau's goal is to restore teachers' authority in a society where it has been diminished by students who overstep their boundaries and parents who overstep their bounds. Or they protect victims.
The bureau's inspectors are vested with broad powers: they harshly resolve conflicts in schools related to violence, the decline of teachers' authority, and the behavior of difficult teenagers.

Bong Geun Dae is an employee of the Bureau (an organization for the protection of teachers' rights)
He's easily recognizable by his "computer genius" image: he's often shown at a computer wearing glasses, tousled hair, and a casual dress code. Specifically, official materials emphasized his "nerd" image, with a distinctive hairstyle and glasses, but without any overly flashy or garish details.
Character
Bong Geun Dae has quite a contrasting image: on the one hand, he is a brilliant analyst, on the other, he is often perceived as a bit naive and clumsy.
There is sincerity and spontaneity in it.

Lim Han Rim is an employee of the Bureau (an organization for the protection of teachers' rights)
Lim Han Rim has a refined, feminine appearance. One of her most striking features is her red hair.
Han Rim's character is a complex contrast between outward fragility and inner strength. On the one hand, she comes across as reserved and even feminine. On the other, she's ready for bold, decisive, and sometimes brutal actions.
Courage and determination. She's not afraid to confront bullies, ready to act decisively and even break the rules for the sake of justice.
Toughness in protecting the weak. Han Rim doesn't just observe problems; she actively intervenes to protect victims of school violence, bullying, and corruption.
Empathetic. Despite her stern exterior, she's not heartless.
She's able to stand up for herself. She has combat experience (she served in the special forces), so she's proficient in various techniques, including using a bamboo sword. However, she's physically inferior to some men, which adds depth to her character.

He is a large, imposing man, and his image clearly conveys the status of a high-ranking official.
Character: Choi Kang-seok is the Minister of Education who founded the Education Rights Protection Bureau (ERPB).
However, his motives are not so simple. On the one hand, he sincerely believes in the bureau's mission—to restore the ruined education system. On the other, he has his own hidden interests, which leaves his character arc ambiguous.
He's confident in his communication, his phrases are polished, and his actions often speak louder than words. He's capable of harshly condemning those who oppose the bureau and try to shut it down, but at the same time, he reflects deeply on how to save the system. In his work, he displays a ruthless demeanor: where talking fails, he resorts to radical, sometimes violent, methods of "education," which he calls "true education."
Gayoon was his daughter, but she died, which is why Choi Kang-seok founded this bureau. Choi Kang-seok knows how moderate Gayoon is, since she was killed by her own student, and Na Hwa-jin also knows that Gayoon was killed by a student.

Na Hwa Jin is an employee of the Bureau (an organization for the protection of teachers' rights).
Build and Hair: A tall, muscular man with long, unkempt black hair. He sometimes ties it back in a ponytail, but most often leaves it loose.
Face and clothing. He has a light stubble—he shaves it periodically, but then grows it out again. At work, he almost always wears a plain black suit, and in his free time, he wears a black T-shirt and black jeans.
Scars. Several scars are visible on the upper body.
Duality. When interacting with friends or solving less serious problems, he can appear quite cheerful and relaxed. But when faced with serious threats—be they cruel students, corrupt teachers, or other dangers to the school system—he transforms: he becomes tough, cold-blooded, and ready to take drastic measures.
Methods. He's not prone to lengthy conversations or formal proceedings. His approach is harsh, often based on the principle of "an eye for an eye": he forces aggressors to experience the same humiliations they inflicted on others. At the same time, the emphasis is on his drive for justice.
He also reacts sharply to jokes made at his expense.
Professional Skills. Before joining the Bureau (a teachers' rights organization), Na Hwa Jin served in the special forces. He is a master of martial arts, possessing quick reflexes, high endurance, and an analytical mind: he gathers information first, examining people's motives before formulating a plan.
His character was deeply shaped by a personal tragedy: the death of Gayoon, his daughter-in-law. This event left a deep emotional scar, and he reacts extremely sensitively to any mention of her. He loved Gayoon dearly, but because Gayoon always interfered in undesirable situations, where others were being bullied, in order to protect the victims, Na Hwa Jin always had to rescue Gayoon a little. But it was precisely because of Gayoon's stubbornness and kind heart that Na Hwa Jin fell in love with her.