Run On

Assistant Director

• 
  Kim Sang Ho

Director

• 
  Lee Jae Hoon

Screenwriter

• 
  Park Si Hyeon

Main Role

• 
  Yim Si Wan

  Ki Seon Gyeom

  Main Role
• 
  Shin Sae Kyeong

  Oh Mi Joo

  Main Role
• 
  Choi Soo Young

  Seo Dan Ah

  Main Role
• 
  Kang Tae Oh

  Lee Young Hwa

  Main Role

Support Role

• 
  Park Young Gyu

  Ki Jung Do [Seon Gyeom's father]

  Support Role
• 
  Cha Hwa Yun

  Yook Ji Woo [Seon Gyeom's mother]

  Support Role
• 
  Ryu Abel

  Ki Eun Bi [Seon Gyeom's sister]

  Support Role
• 
  Yeon Je Wook

  Jung Ji Hyun [Dan Ah's assistant]

  Support Role
• 
  Lee Bong Ryun

  Park Mae Yi [Mi Joo's friend]

  Support Role
• 
  Lee Jung Ha

  Kim Woo Shik [Seon Gyeom's track team junior]

  Support Role
• 
  Park Sung Joon

  Kwon Young Il [Seon Gyeom's friend]

  Support Role
• 
  Lee Hwang Ui

  Seo Myung Pil [Dan Ah's father]

  Support Role
• 
  Choi Jae Hyun

  Seo Tae Woong [Dan Ah's step-brother]

  Support Role
• 
  Lee Shin Ki

  Seo Myung Min [Dan Ah's step-brother]

  Support Role
• 
  Seo Jae Hee

  Dong Gyeong [Dann Agency's director]

  Support Role
• 
  Kim Dong Young

  Go Ye Joon [Young Hwa's friend]

  Support Role
• 
  Kim Si Eun

  Go Ye Chan [Ye Joon's sister]

  Support Role
• 
  Cha Bo Sung

  Lucian [Tae Woong' band mate]

  Support Role
• 
  Seo Jin Won

  [Seon Gyeom's coach]

  Support Role
• 
  Kim Shi Young

  [Coffee shop owner]

  Support Role

Guest Role

• 
  Bong Joon Ho

  [Himself] (Ep. 1)

  Guest Role
• 
  Kim Jung Ho

  Hwang Guk Geon [Professor] (Ep. 1)

  Guest Role
• 
  So Yun Ho

  [Police officer] (Ep. 1)

  Guest Role
• 
  Kim Ye Won

  Choi Tae Ri [Actress] (Ep. 1-3, 16)

  Guest Role
• 
  Park Sang Won

  Park Gyu Deok [Seon Gyeom's track team junior] (Ep. 1-4, 6)

  Guest Role
• 
  Na Ji Hoon

  Kim Gi Beom [Seon Gyeom's track team junior] (Ep. 1-4, 6)

  Guest Role
• 
  Kim Yong Ho

  [Assistant coach] (Ep. 1-4, 6)

  Guest Role
• 
  Bae Yoo Ram

  Han Seok Won [Mi Joo's ex-boyfriend] (Ep. 1 & 16)

  Guest Role
• 
  Ahn Jae Jun

  [Athlete] (Ep. 2)

  Guest Role
• 
  Kim Min Sang

  [Tae Ri's manager](Ep. 2-3, 16)

  Guest Role
• 
  Yoon Tae Hee

  [Maid] (Ep. 3)

  Guest Role
• 
  Kim Mi Hye

  Yoo Ah In [Reporter] (Ep. 3-4)

  Guest Role
• 
  Son Young Soon

  Shin Ah Ryeon [Woo Shik's grandmother] (Ep. 3, 5, 10, 16)

  Guest Role
• 
  Park Jung Eon

  [Disciplinary judge] (Ep. 3 & 6)

  Guest Role
• 
  Kim Do Young

  [Disciplinary judge] (Ep. 3, 6)

  Guest Role
• 
  Lee Jae Woo

  [Disciplinary judge] (Ep. 3, 6)

  Guest Role
• 
  Geum Hae Na

  [Boxer] (Ep. 4)

  Guest Role
• 
  Bret Allan Lindquist

  Rob Stark [Reporter] (Ep. 4-5)

  Guest Role
• 
  Lee Soo Bin

  Lee Soo Bin [Track team girl] (Ep. 4, 7, 11, 13, 16)

  Guest Role
• 
  Jung Myung Joon

  [Priest] (Ep. 5)

  Guest Role
• 
  Ok Joo Ri

  [Church member] (Ep. 5)

  Guest Role
• 
  Jo Yoo Jung

  [Church member] (Ep. 5)

  Guest Role
• 
  Shim Young Eun

  Yoon Gong Ju [Mi Joo's college friend] (Ep. 5)

  Guest Role
• 
  Lee Do Yeop

  No Geun Seong [Assemblyman] (Ep. 5-6, 12)

  Guest Role
• 
  Park Joo Hee

  Hui Jin [Producer] (Ep. 5, 7-9, 16)

  Guest Role
• 
  Kim Na Young

  Cho Hye Won [May's employee] (Ep 5, 7, 11)

  Guest Role
• 
  Kim Kyung Ae

  [Restaurant owner] (Ep. 5 & 11)

  Guest Role
• 
  Seo Jung Yeon

  Bang Bae Jeong [Track & Field coach] (Ep. 6-7)

  Guest Role
• 
  Park Joo Yong

  [Tae Woong's manager] (Ep. 7, 9-10, 13, 16)

  Guest Role
• 
  Lee Won Hee

  Quentin Park [Director] (Ep. 8)

  Guest Role
• 
  Je Seung Hyun

  [Hairstylist] (Ep. 8)

  Guest Role
• 
  Lee Moo Nyoung

  [Convenience store owner] (Ep. 8)

  Guest Role
• 
  Park Gi Seon

  [Doctor] (Ep. 8)

  Guest Role
• 
  Garrison Michael Farquharson-Keener

  [Cinematographer] (Ep. 8-9)

  Guest Role
• 
  Kim Jae Hwa

  Yeom Gang sun / "Julie Yeom" [Producer] (Ep. 8-9)

  Guest Role
• 
  Kim Won Hae

  [Bartender] (Ep. 8, 16)

  Guest Role
• 
  Park Jin Young

  [May's employee] (Ep. 11)

  Guest Role
• 
  Park Joon Sang

  [Manager of Jieum Construction Track Team] (Ep. 13)

  Guest Role
• 
  Kim Seon Ho

  Kim Sang Ho [Film director] (Ep. 16)

  Guest Role
• 
  Kim In Kyung

  [Staff] (Ep.1)

  Guest Role
• 
  Jung Min Joo

  Min Ju

  Guest Role
• 
  Kim Soo Jung

  [Myeong Pil's second wife] (Ep. 12)

  Guest Role
• 
  Kim Chae Won

  [Team staff] (Ep. 14)

  Guest Role
• 
  Yang Yoon Hee

  [Chang Seop's mother] (Ep. 13)

  Guest Role
• 
  Lee Chang Won Guest Role
• 
  Koo Do Kyun

  [Shop owner] (Ep. 13)

  Guest Role
• 
  Kang Choon Sung

  [Photographer] (Ep. 3 - 4)

  Guest Role
• 
  Jung Soon Mi

  [Pureun Keunsol School faculty]

  Guest Role
• 
  Kim Wang Yong

  [Mayor] (Ep. 9)

  Guest Role
• 
  Choi Min Kyu

  [PE student] (Ep. 5)

  Guest Role
• 
  Kim Young Joon

  [Ji Woo's assistant]

  Guest Role
• 
  Park Ji Won

  [Pharmacist] (Ep. 13)

  Guest Role
• 
  Kim Ki Ryung

  [Jeweler] (Ep. 5)

  Guest Role
• 
  Park Joo Ha

  [Grocery store crying girl] (Ep. 5)

  Guest Role
• 
  Ji Yun Seong

  [James' boyfriend (ep.9)]

  Guest Role
• 
  Ji Han Ah

  [Soo Bin's aunt] (Ep. 13)

  Guest Role

Unknown

• 
  Lee Ji Hyun Unknown