She's on Duty

Kang No-young, boy at school, Jae-in's neighbour

Class teacher

Detective Cho

Math Teacher (cameo)

Detective Kang

Cha Young-Jae, second mob boss, Seung-Hee's father

Detective Chun, Jae-in's uncle and boss

Bae Doo-Sang, mob boss of the Whacker gang

Chun Jae-in, undercover cop

Jo Hye-ryung