A boisterous detective goes undercover in a high school in order to befriend the teenage daughter of a notorious gangster.
Chun Jae-in, undercover cop
Kang No-young, boy at school, Jae-in's neighbour
Seung-Hee, daughter of mob boss
Detective Kang
Detective Chun, Jae-in's uncle and boss
Jo Hye-ryung
Bae Doo-Sang, mob boss of the Whacker gang
So-young, girl in class who wants Jae-in's protection
Class teacher
Cha Young-Jae, second mob boss, Seung-Hee's father