Na Hwa-jin is a former special-forces soldier who later joins the Educational Rights Protection Bureau to combat violence and injustice in schools. His life is deeply affected by the tragic death of his fiancée, Choi Ga-yoon, a dedicated teacher who was killed by a violent student. Her death leaves Hwa-jin devastated and becomes the main reason he dedicates himself to protecting teachers and students from abuse and bullying. He is tall, athletic, and usually wears formal suits, giving him a serious and intimidating appearance. As the bureau's lead inspector. Has black hair dark eyes. Hwa-jin uses his intelligence, discipline, and combat skills to bring justice to schools and prevent others from suffering the same fate as Ga-yoon. Maybe he can start his life all over again. Currently he is light hearted, dry, nonchalant and very strong because of the 707 marine crops trainings.

Im Han-rim is a fierce, unpredictable field inspector for the Educational Rights Protection Bureau and a former Special Forces sergeant who acts as the ultimate "loose cannon" against school bullies. Expertly skilled in Jeet Kune Do and weapons martial arts, she bypasses slow bureaucratic rules with a "short deliberation, fast action" mindset, using psychological intimidation, physical dominance, and undercover disguises to completely neutralize violent students and corrupt parents alike. Has long black silky hair, dark eyes and is slim.

Choi Kang-seok is the authoritative, politically powerful Minister of Education who secretly spearheads the Educational Rights Protection Bureau (ERPB) to combat severe school violence with law-bending discipline. His fierce vigilantism is fueled by an intense personal tragedy from two years prior, when his schoolteacher daughter, Choi Ga-yoon, was brutally murdered by her own student. He's broad, masculine and older.

Bong Geun-dae is a nerdy, lovable civil servant and two-year KAIST university graduate who provides vital tech support and intelligence for the Educational Rights Protection Bureau. As a naive yet dedicated deputy manager, he works behind the scenes alongside field inspectors to track down violent school bullies and expose corrupt administrators.