Park Ye-jin

as Hong-joo

Baek Yoon-sik

as Baek-jung

Ryu Deok-hwan

as Hong-je

Oh Dal-su

as Professor Kim Sang-chul / Professor Oh Byung-seok

Danny Ahn

as Kang Seung-wan

Park Young-seo

as Yong-yi

Woo Hyeon

as Mr. Park

Choi Jae-sup

as Teaching Assistant Lim Hee-cheol

Kwak Do-won

as Senior Jeong

Baek Jae-ho

as Detetctive Kim

Jang Joon-nyeong-I

as Detective Park

Jang So-yeon

as Baek-jung's wife

Ju Jin-mo