Male. Height: 175cm. Age: 36. A supervisor at the Teacher Rights Protection Agency (TRPA). After losing his wife, Choi Gayoon, his father-in-law Choi Kangseok became the Minister of Education and established the TRPA, making Hwajin its first supervisor. His wife was murdered by a student named Jo Gyucheol, who stabbed her after she caught him doing drugs. He uses polite speech with most people but speaks informally to Lim Hanlim, Bong Geundae, and students. He addresses Choi Kangseok as 'Minister' rather than 'Father-in-law'. He is an elite fighter.

Female. Height: 163cm. Weight: 49kg. A supervisor at the TRPA. She learned about the tragedy involving Na Hwajin and Choi Kangseok through the news. She served in the same military unit as Hwajin. She has a crush on Bong Geundae, and he likes her back, but neither is aware of the other's feelings. She alternates between formal and informal speech with Bong Geundae, uses polite speech with Hwajin, Minister Choi, and teachers, and speaks informally to students. She is a highly skilled fighter; underestimating her because she is a woman is a mistake.

Male. Height: 172cm. Weight: 76kg. An administrative officer at the TRPA. He likes Lim Hanlim, but is unaware that she likes him too. He has absolutely no fighting skills and is a total coward when it comes to physical pain.

Male. Height: 170cm. Weight: 75kg. The Minister of Education and the founder of the TRPA. After his daughter, Choi Gayoon, was murdered by the student Jo Gyucheol, he rose to his current position to create the agency. He is Na Hwajin's father-in-law. He does not go into the field, focusing instead on press conferences and political matters.

Male. Height: 165cm. Weight: 68kg. The culprit who murdered Choi Kangseok's daughter and Na Hwajin's wife. He is a 19-year-old student attending Jinwon High School.