Ha Jung-woo

as Goo Joo-wol / Detective Ma Dong-wook

Gong Hyo-jin

as Lee Hee-jin / Kim Hae-young

Yoo In-na

as Soo-jung / Kyung-sook

Jo Hee-bong

as Publisher Kwak / Detective Squad Chief Kwak

Lee Byung-joon

as M

Ji Jin-hee

as Goo Joo-ro

Kwak Do-won

as Director Hwang

Seo Hyun-woo

as Yi-gyu

Son Byeong-uk

as Juwol's Homeroom Teacher

Jeon Su-ji

as Art Teacher

Choi Won-tae

as Baek Sun-il

Kim Jae-hwa

as Joo-hee

Park Jun-myun

as Baek Sun-young

Lee Jun-hyeok

as Professor Jeong

Teo Yoo

as Secretary

Kim Ji-hoon

as Detective

Park Young-soo

as Young-shik / President Jo