as Chun Jae-in, undercover cop

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

as Seung-Hee, daughter of mob boss

as Detective Kang

as Detective Chun, Jae-in's uncle and boss

as Jo Hye-ryung

as Bae Doo-Sang, mob boss of the Whacker gang

as So-young, girl in class who wants Jae-in's protection

as Class teacher

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

as Detective Cho

as cameo

as Math Teacher (cameo)

as Ja-gyeong