She's on Duty

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

Detective Cho

Detective Kang

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

Chun Jae-in, undercover cop

Math Teacher (cameo)

Bae Doo-Sang, mob boss of the Whacker gang

Class teacher

Seung-Hee, daughter of mob boss

Detective Chun, Jae-in's uncle and boss