Chun Jae-in, undercover cop
Kim Sun-a
Kang No-young, boy at school, Jae-in's neighbour
Gong Yoo
Seung-Hee, daughter of mob boss
Nam Sang-mi
Detective Kang
Kim Sang-ho
Detective Chun, Jae-in's uncle and boss
Noh Joo-hyun
Bae Doo-Sang, mob boss of the Whacker gang
Oh Kwang-rok
So-young, girl in class who wants Jae-in's protection
Moon Seo-yeon
Class teacher
Park Sang-myeon
Cha Young-Jae, second mob boss, Seung-Hee's father
Kim Kap-soo
Detective Cho
Ha Jung-woo