Supporting
Song Geon-hee as Lee Ki-beom / Cha Young-beom
Lee Ki-beom: Ki-hwan's younger brother and Sun-young's boyfriend.
Cha Young-beom: Ki-beom and Sun-young's son who is an intern at Noise Cut.
Seo Ji-hye as Kang Sun-young
An elementary school teacher who is Tae-joo's younger sister and Ki-beom's girlfriend.
Jung Moon-sung as Lee Ki-hwan
The owner of Kangseong Bookstore who is Tae-joo and Ji-won's childhood friend, and Ki-beom's older brother.
Ryu Hae-jun as Park Dae-ho
A rookie detective at Kangseong Police Station. He assists Tae-joo on investigations and works alongside his senior officers.
Hur Jung-do as Cha Joon-young
Si-young's half-brother and a high-ranking police official who later gets appointed as the chief of the Kangseong Police Station.
Baek Hyun-jin as Kim Man-chun
Team Leader at Kangseong Police Station
Jeon Jae-hong as Jang Myung-do
A corrupt detective at Kangseong Police Station who is in cahoots with Si-young.
Kim Eun-woo as Do Hyung-gu
A corrupt detective at Kangseong Police Station who is in cahoots with Si-young.
Baek Seung-hwan as Im Seok-man
Ki-beom's friend who is cripple.
Sung Yeo-jin as Ki-beom's mother
Lim Yun-bi as Jeong-sook
Ki-Hwan's wife.
Kil Eun-sung as Park Sang-beom
Kim Joon-hee as teen Sang-beom
The owner of Modoka's Bar and a gangster.
Lee Ji-hye as Lee Sook-hee
A policewoman at Kangseong Police Station.
Hong Bi-ra as Kim Hee-jin
Si-young's fiancé and Chairman Kim's daughter.
Lee Suk-hyeong as Un-hui
A cameraman at Kangseong Daily and Ji-won's assistant.
Park Sang-hoon as Lee Sung-jin
A former offender with a criminal record for stealing stockings.
Kim Hwan-hee as Kim Min-ji
A high school student who is Jeong-rin's friend and the sixth victim of the serial murder case.
Kong A-reum as Yu Jeong-rin
A high school student who is Min-ji's friend and the fourth victim of the serial murder case.
Moon Kyung-cho as Park Kyeong-sik
Ki-beom's friend who got married.
Yoo Seung-mok as Cha Mu-jin
Si-young's father, a powerful politician and former military general who has long held significant influence in Kangseong.
Kang Jeong-woo as Jeon Kyung-ho
An elementary school teacher and the nephew of Kangseong Governor.
Hwang Eun-hoo as Park Ae-sook
A survivor of the serial murder case.
Kim Gye-rim as Kim Mi-yeon
A survivor of the serial murder case.
Park Sung-hoon as Hwang Jae-hoo
A prosecutor.
