Inspector Koo

Composer

• 
  Kim Tae Seong

Director

• 
  Lee Jung Heum

Editor

• 
  Shin Min Kyung

Screenwriter

• 
  Sung Cho Yi

Main Role

• 
  Lee Young Ae

  Koo Kyung Yi

  Main Role
• 
  Kim Hye Joon

  Song Yi Kyung

  Main Role
• 
  Kim Hae Sook

  Chief Yong Sook

  Main Role
• 
  Kwak Sun Young

  Na Je Hee

  Main Role
• 
  Baek Sung Chul

  Santa

  Main Role
• 
  Jo Hyun Chul

  Oh Kyung Soo

  Main Role

Support Role

• 
  Lee Hong Nae

  Ahn Keon Wook [K's helper]

  Support Role
• 
  Bae Hae Seon

  Jung Jeong Yeon

  Support Role
• 
  Choi Dae Chul

  Heo Seong Tae

  Support Role
• 
  Park Ji Bin

  Heo Hyun Tae

  Support Role
• 
  Jung Suk Yong

  Director Kim

  Support Role
• 
  Choi Young Joon

  Jang Seong Woo [Kyung Yi's husband]

  Support Role
• 
  Jung Jong Joon

  Na Jong Jun [Na Je Hee's Father]

  Support Role
• 
  Choi So Yool

  Na Na [Na Je Hee's Daughter]

  Support Role
• 
  Park Kang Sub

  Dae Ho

  Support Role
• 
  Lee Han Ju

  Lee Yeong Ju

  Support Role

Guest Role

• 
  Bae Myung Jin

  ['NT Life Insurance' Team A member] (Ep. 1)

  Guest Role
• 
  Lee Jin Seung

  [JBS reporter] (Ep. 1)

  Guest Role
• 
  Lee So Geum

  [Food deliveryman] (Ep. 1)

  Guest Role
• 
  Jeon Seok Chan

  [Detective] (Ep. 1-2)

  Guest Role
• 
  Lee Dong Wook

  [Man fishing] (Ep. 1-2)

  Guest Role
• 
  Ahn Ryeo Jin

  [Escort] (Ep. 1-2)

  Guest Role
• 
  An Tae Rin

  Kim Seon Mi (Ep. 1-2, 4)

  Guest Role
• 
  Park Ye Young

  Yoon Jae Young (Ep. 1-2, 4)

  Guest Role
• 
  Kim Oh Bok

  Kim Won Shik [Inspection Team A Member] (Ep. 1-2, 6)

  Guest Role
• 
  Kang Hak Soo

  [Janitor] (Ep. 1, 5-6)

  Guest Role
• 
  Kim Kang Hyun

  Kim Min Kyu (Ep. 1-2, 6, 10)

  Guest Role
• 
  Park Yong

  [Client with back pain] (Ep. 2)

  Guest Role
• 
  Jang Jae Ha

  [Hansel] (Ep. 2)

  Guest Role
• 
  Lim Soo Jung

  Gretel (Ep. 2)

  Guest Role
• 
  Kim Ha Eon

  [Boy] (Ep. 2)

  Guest Role
• 
  Choi Hee Jin

  Son Ji Yu [Psychiatrist] (Ep. 2, 5)

  Guest Role
• 
  Park Jeong Min

  [Apartment security guard] (Ep. 2, 9)

  Guest Role
• 
  Yoo Pil Ran

  ['NT Life Insurance' manager] (Ep. 3)

  Guest Role
• 
  Shin Yoon Seop

  Park Kyu Il (Ep. 3)

  Guest Role
• 
  Choi Ha Yoon

  Yoon Mi Ae (Ep. 3)

  Guest Role
• 
  Kim Hong Kyo

  [Red sneakers guy] (Ep. 3)

  Guest Role
• 
  Lee Joong Ok

  [Medical examiner] (Ep. 3)

  Guest Role
• 
  Ku Dong Hoon

  [Medical examiner] (Ep. 3)

  Guest Role
• 
  Cho Yi Hyun

  [Bubble's event organizer] (Ep. 3)

  Guest Role
• 
  Ha Seung Yeon

  ['Sunshine' dormitory staff] (Ep. 3)

  Guest Role
• 
  Seo Jung Bin

  [Gas station customer] (Ep. 3)

  Guest Role
• 
  Do Mi Yeon

  [Used camera buyer] (Ep. 3)

  Guest Role
• 
  Lee Jeong Chan

  (Ep. 3)

  Guest Role
• 
  Song Hoon

  ['MEK Security' employee] (Ep. 3, 9)

  Guest Role
• 
  Jo Si Yeon

  Su Yeon (Ep. 4)

  Guest Role
• 
  Park Noh Shik

  [Bird guy] (Ep. 4)

  Guest Role
• 
  Kim Kwang Suk

  [Detective] (Ep. 4)

  Guest Role
• 
  Han Seung Yoon

  [Policeman] (Ep. 4)

  Guest Role
• 
  Jang Sung Kyu

  [Policeman] (Ep. 4)

  Guest Role
• 
  Min Eung Shik

  [Doll expert] (Ep. 4)

  Guest Role
• 
  Noh Hee Joong

  [Security guard] (Ep. 4)

  Guest Role
• 
  Joo Boo Jin

  [Subway passenger] (Ep. 4)

  Guest Role
• 
  Yoon Boo Jin

  [Jung Yeon's co-worker] (Ep. 4)

  Guest Role
• 
  Jeong Seo Yeon

  [Jeong Yeon's co-worker] (Ep. 4)

  Guest Role
• 
  Kim Bong Su

  [Senior citizen playing go] (Ep. 4-5)

  Guest Role
• 
  Kim Soo Ro

  Ko Dam (Ep. 4, 6-7)

  Guest Role
• 
  Park Ye Ni

  [Yi Kyung's Mother] (Ep. 5)

  Guest Role
• 
  Lee Hyun Jin

  [Yi Kyung's Father] (Ep. 5)

  Guest Role
• 
  Jeong Seo A

  Song Yi Kyung [Child] (Ep. 5)

  Guest Role
• 
  Sung Hyun Mi

  [Cleaning lady] (Ep. 5)

  Guest Role
• 
  Chu Jung Hun

  [ATV rental employee] (Ep. 5)

  Guest Role
• 
  Cha Ye Jun

  [Woo Yeon's friend] (Ep. 5)

  Guest Role
• 
  Won Geun Hee

  [Monk] (Ep. 5, 10)

  Guest Role
• 
  Jun Joon Woo

  [Police officer] (Ep. 6)

  Guest Role
• 
  Park Sun Young

  [KD Peace Lab employee] (Ep. 6)

  Guest Role
• 
  Kam Rain

  [KD Peace Lab employee] (Ep. 6)

  Guest Role
• 
  Gi Hwan

  [KD Peace Lab employee] (Ep. 6)

  Guest Role
• 
  Kang Gu Ha

  [KD Peace Lab employee] (Ep. 6)

  Guest Role
• 
  Ahn Shin Woo

  [Security team captain] (Ep. 7)

  Guest Role
• 
  Lee Chae Hyun

  [Hospital boy] (Ep. 7)

  Guest Role
• 
  Park Byung Wook

  [Bomb parcel supplier] (Ep. 7)

  Guest Role
• 
  Choi Sol Hui

  [Drunk diner] (Ep. 8)

  Guest Role
• 
  Jang Jae Kwon

  [Heo Seong Tae's campaign staff] (Ep. 8)

  Guest Role
• 
  Jeong Yoon Hee

  [Na Je Hee's colleague] (Ep. 8)

  Guest Role
• 
  Min Jae

  [Hotel employee] (Ep. 8)

  Guest Role
• 
  Jung Mi Kyung

  [Restaurant owner] (Ep. 8)

  Guest Role
• 
  Park Mu Yeom

  [Photographer] (Ep. 9)

  Guest Role
• 
  Jo Jae Ryong

  Park Du Mok (Ep. 9)

  Guest Role
• 
  Jo Sung Joon

  Lee Jun Hyun (Ep. 9-10)

  Guest Role
• 
  Kim Ki Cheon

  [Caretaker] (Ep. 9-10)

  Guest Role
• 
  Lee Jae Eun

  [Keon Wook's neighbor] (Ep. 9-10)

  Guest Role
• 
  Kim Seo Jung

  [Heo Hyeon Tae's lover] (Ep. 9-11)

  Guest Role
• 
  Seo Dong Won

  Kwak [Reporter] (Ep. 9-12)

  Guest Role
• 
  Park Joo Ha

  [Railway platform girl] (Ep. 10)

  Guest Role
• 
  Nam Dong Ha

  [Sound engineering expert] (Ep. 11)

  Guest Role
• 
  Kim Mi Ra

  Ms. Won (Ep. 11)

  Guest Role
• 
  Han Ki Jang

  [Temple guard] (Ep. 11)

  Guest Role
• 
  Yeon Je Hun

  [Press conference staff] (Ep. 11)

  Guest Role
• 
  Kang Chung Hun

  [JBS anchorman] (Ep. 11)

  Guest Role
• 
  Yoo Young Bok

  [Jong Jun's friend] (Ep. 11)

  Guest Role
• 
  Son Dong Soo

  [News program panelist] (Ep. 11)

  Guest Role
• 
  Lee Yoon Sang

  Minister Kim (Ep. 11-12)

  Guest Role
• 
  Bae Hyun Kyung

  Kim Hwan Hui [Prosecutor] (Ep. 11-12)

  Guest Role
• 
  Han Yeo Wool

  [Baby murderer] (Ep. 11-12)

  Guest Role
• 
  Yong Jin

  [Briquette murderer] (Ep. 11-12)

  Guest Role
• 
  Oh Se Il

  [Blackmailed person] (Ep. 11-12)

  Guest Role
• 
  Kim Sung Gon

  [Blackmailed person] (Ep. 11-12)

  Guest Role
• 
  Park Jin Sung

  [Blackmailed person] (Ep. 11-12)

  Guest Role
• 
  Lee Eui Ryung

  [Deliveryman] (Ep. 3)

  Guest Role
• 
  Park Joo Won

  [Song Yi Kyung's high school friend]

  Guest Role
• 
  Go Jin Myung

  [Yi Kyung's neighbor] (Ep. 5)

  Guest Role
• 
  Lee Yu Ju

  [Agent]

  Guest Role
• 
  Lim Jin Woong

  Jin Mo (Ep. 2)

  Guest Role
• 
  Kang Ro Chae

  [Blackmailed person] (Ep. 11-12)

  Guest Role
• 
  Kim Joon Hee

  [Detective] (Ep. 12)

  Guest Role
• 
  Jeon Yeo Jin

  [Prosecutor] (Ep. 12)

  Guest Role
• 
  Eom Ji Man

  [Prosecutors' office staff] (Ep. 12)

  Guest Role
• 
  Kang Seo Kyung

  Han Gyeol

  Guest Role
• 
  Choi Young In

  [Mountainside restaurant worker]

  Guest Role
• 
  Jeon Jeong Il

  [Cleaner]

  Guest Role

Unknown

• 
  Lee Ru Da Unknown
• 
  Kim Young Hee Unknown
• 
  Choi Da Eum Unknown