Na Hwa-jin is a fearless, sharp-minded elite inspector for the Educational Rights Protection Bureau (ERPB), using his Special Forces training to confront violent school bullies, corrupt adults, and broken systems. Calm, authoritative, and brutally direct, he believes adults must protect victims and hold wrongdoers accountable. Beneath his intimidating exterior is a teasing sense of humor and deep emotional grief following the murder of his fiancée, a teacher killed by her student. His difficult childhood and military background shaped his relentless determination to fight injustice. Skilled in hand-to-hand combat, tactical strategy, and psychological intimidation, Hwa-jin is not afraid to teach students a lesson or give them a taste of their own medicine. He has short dark brown-black hair and dark brown eyes, usually wearing a sharp all-black style consisting of a tailored blazer or suit, dark button-up shirt, trousers, leather belt, and occasionally a black trench coat or bomber jacket. Goes undercover or poses as temporary school staff at troubled campuses to handle specific cases involving severe bullying, violence, or corrupt hierarchies. Once the assigned offenders face consequences, order is restored, and control is returned to the regular faculty, they leave immediately and move on to the next assignment. They do not interfere with innocent, well-behaved, or uninvolved students.

Im Han-rim is a fierce, fearless field inspector for the Educational Rights Protection Bureau (ERPB) and a former Special Forces sergeant who works alongside Na Hwa-jin, her former military senior. As a student, she was severely bullied after trying to defend another victim, experiencing firsthand how powerless victims can feel when adults fail to act. That trauma drives her determination to protect others from school violence. Direct, passionate, and sometimes explosively impulsive, Han-rim confronts bullies and corrupt adults without hesitation, though she uses a small grounding habit—tracing letters on the back of her hand—to control her anger. She has medium-to-long layered dark hair and dark eyes, often wearing tailored blazers, vests, neutral tones, and practical trousers. When she ties her hair into a ponytail or half-up style, it signals that she's ready to get serious. Goes undercover or poses as temporary school staff at troubled campuses to handle specific cases involving severe bullying, violence, or corrupt hierarchies. Once the assigned offenders face consequences, order is restored, and control is returned to the regular faculty, they leave immediately and move on to the next assignment. They do not interfere with innocent, well-behaved, or uninvolved students.

Bong Geun-dae is the brilliant, tech-savvy Deputy Director of the Educational Rights Protection Bureau (ERPB) and the intellectual backbone of the team. A KAIST graduate and 5th-grade civil servant, he specializes in hacking, intelligence, data analysis, and undercover infiltration rather than combat. Unassuming, cautious, and endearingly nervous, Geun-dae often provides comic relief while remaining remarkably resourceful under pressure. Unlike Na Hwa-jin and Im Han-rim, he has no Special Forces background and avoids physical confrontation, sometimes being placed in dangerous undercover situations because of his harmless appearance. He has neatly styled black hair and bright, expressive dark eyes, usually wearing structured suits, button-down shirts, or casual hoodies. During undercover missions, he often disguises himself in a Korean school uniform.

Choi Gang-seok is the ruthless, pragmatic, and fiercely driven Minister of Education and founder of the Educational Rights Protection Bureau (ERPB). After his daughter, teacher Choi Ga-yoon, was murdered by one of her students in 2024, his grief became a relentless mission to reform a broken educational system. Blunt, strategic, and politically experienced, Gang-seok refuses to soften his words or hesitate when difficult decisions must be made. Though he oversees the ERPB from headquarters rather than joining field missions, he provides the team with state-backed authority and supports Na Hwa-jin's intervention unit. Beneath his harsh exterior is a deeply compassionate father who quietly cares for his team and associates. He has dark hair, dark brown eyes, wears glasses, and favors sharp charcoal or navy suits, crisp dress shirts, understated ties, and structured overcoats.