The One and Only

Director

• 
  Oh Hyun Jong

Screenwriter

• 
  Moon Jung Min

Main Role

• 
  Ahn Eun Jin

  Pyo In Suk

  Main Role
• 
  Kim Kyung Nam

  Min Woo Cheon

  Main Role
• 
  Kang Ye Won

  Kang Se Yeon

  Main Role
• 
  Joy

  Seong Mi Do

  Main Role

Support Role

• 
  Go Doo Shim

  Yook Seong Ja [In Suk's grandmother]

  Support Role
• 
  Jang Hyun Sung

  Pyo Kang Seon [In Sook's father]

  Support Role
• 
  Seo Yeon Woo

  Ha San A [In Sook's neighbor]

  Support Role
• 
  Cha Hee

  Woo Kyung Mi [San A's mother]

  Support Role
• 
  Do Sang Woo

  Cho Shi Young [Regional Investigation Unit Inspector / Special Crime Squad]

  Support Role
• 
  Lee Bong Ryun

  Hwang Ma Jin [Regional Investigation Unit Team Leader/ Special Crime Squad]

  Support Role
• 
  Jang In Sub

  Oh Jin Gyu [Regional Investigation Unit Sergeant / Special Crime Squad]

  Support Role
• 
  Han Geon Yu

  Gu Ji Pyo [Mi Do's boyfriend / LE Group Director]

  Support Role
• 
  Han Kyu Won

  Oh Young Chan [Se Yeon's husband]

  Support Role
• 
  Ahn Chang Hwan

  Shin Tae Il

  Support Role
• 
  Choi Young Woo

  Park Seung Seon

  Support Role
• 
  Lee Soo Mi

  Sister Magdalena [Director, Morning Light Hospice]

  Support Role
• 
  Yoon Bo Ra

  Sister Veronica [Morning Light Hospice]

  Support Role
• 
  So Hee Jung

  Moon Young Ji [Morning Light Hospice]

  Support Role
• 
  Kim Soo Hyung

  Lim Ji Hoo [Young Ji's daughter]

  Support Role
• 
  Lee Hang Na

  Choi Sung Hae [Morning Light Hospice]

  Support Role
• 
  Joo In Young

  Cha Yeo Wol [Morning Light Hospice]

  Support Role
• 
  Seong Byung Sook

  Oh Cheon Deok [Morning Light Hospice]

  Support Role
• 
  Kim Byung Chun

  Dr. Cho [Morning Light Hospice]

  Support Role
• 
  Kim Jung Hwan

  Kang Seo Goon [Morning Light Hospice]

  Support Role
• 
  Jang Seo Won

  Jo Woong Do [Morning Light Hospice]

  Support Role
• 
  Jeon Yi Soo

  Ho Sun

  Support Role

Guest Role

• 
  Park Eun Young

  [Bathhouse manager] (Ep. 1)

  Guest Role
• 
  Yoon Boo Jin

  [Bathhouse scrubber] (Ep. 1)

  Guest Role
• 
  Lee Jae Eun

  [Bathhouse scrubber] (Ep. 1)

  Guest Role
• 
  Kim Geum Soon

  [Bathhouse customer] (Ep. 1)

  Guest Role
• 
  Ryu Yeon Seok

  Dr. Yoo Ho Joon (Ep. 1)

  Guest Role
• 
  Jung Il Hwa

  [In Sook's mother] (Ep. 1)

  Guest Role
• 
  Jung Se Hyun

  [Sung Hae's daughter] (Ep. 1)

  Guest Role
• 
  Yoo Chae Yeon

  Eun Bi [Tae Il's daughter] (Ep. 1, 4)

  Guest Role
• 
  Lee Nam Gyeong

  Pyo In Sook [Child] (Ep. 1-8)

  Guest Role
• 
  Baek Hyun Jin

  Ha Young Geun

  Guest Role
• 
  Oh Min Ae

  [Young Chan's mother] (1-2, 7, 11, 14)

  Guest Role
• 
  Yoon Bok In

  [Se Yeon's mother] (Ep. 1, 3, 7-8, 12, 15)

  Guest Role
• 
  Choi Hye Seo

  [Passerby daughter] (Ep. 2)

  Guest Role
• 
  Ahn Hye Won

  [Pharmacist] (Ep. 2)

  Guest Role
• 
  Park Se In

  [Vet, Local Animal Hosp.] (Ep. 2-3)

  Guest Role
• 
  Moon Seo Yeon

  [Swimming pool bully] (Ep. 2, 4)

  Guest Role
• 
  Jung Hyun Joon

  Min Woo Cheon [Child] (Ep. 2-8)

  Guest Role
• 
  Kim Ji Yul

  Seong Mi Do [Child] (Ep. 2, 10)

  Guest Role
• 
  Oh Ki Hwan

  [Mi Do's father] (Ep. 2, 10)

  Guest Role
• 
  Veronica Seo

  [Mi Do's mother Young] (Ep. 2, 10)

  Guest Role
• 
  Kim Seo Jun

  Seong Min Woong [Mi Do's brother] (Ep. 2, 10, 16)

  Guest Role
• 
  Han Dong Hee

  [Woo Cheon's mother] (Ep. 3-4, 8)

  Guest Role
• 
  Lee Joo Young

  Cha Myung Joo [Eun Hyuk's mother] (Ep. 3, 5, 12)

  Guest Role
• 
  Ok Joo Ri

  [Neighborhood woman] (Ep. 4)

  Guest Role
• 
  Choi Min Geum

  [Food stall vendor] (Ep. 4, 8)

  Guest Role
• 
  Moon Seong Hyun

  Min Woo Cheon [Young] (Ep. 4-5, 8, 12)

  Guest Role
• 
  Lee Seung Joon

  [Guseong Gang member] (Ep. 4-5, 9, 12)

  Guest Role
• 
  Son Hwa Young

  [Guseong Gang member] (Ep. 4, 12, 14)

  Guest Role
• 
  Hwang Dae Woong

  [Guseong Gang member] (Ep. 4, 12, 14)

  Guest Role
• 
  Park Jin Young

  [NFS technician] (Ep. 5, 8)

  Guest Role
• 
  Jeong Young Do

  Reporter Park (Ep. 6)

  Guest Role
• 
  Lee Ji Young

  [Reporter] (Ep. 6, 9-10, 13)

  Guest Role
• 
  Kim Jang Hwan

  [Reporter] (Ep. 6, 9-10, 13)

  Guest Role
• 
  Park Ji Ho

  [Reporter] (Ep. 6, 9-10, 13)

  Guest Role
• 
  Park Se Hee

  Kang Se Yeon [Child] (Ep. 6, 15)

  Guest Role
• 
  Kim Su A

  Moon Young Ji [Child] (Ep. 7)

  Guest Role
• 
  Lee Young Jin

  Ji Yoon Seo [Attorney] (Ep. 7, 9-12, 14)

  Guest Role
• 
  Jeon Noh Min

  [Gu Ji Pyo's father / Le Group executive] (Ep. 7, 11, 13, 16)

  Guest Role
• 
  Yoon Joo Man

  [Cellphone technician] (Ep. 8, 10-11, 14)

  Guest Role
• 
  Lee Dong Gyu

  [JSH anchorman] (Ep. 8, 10, 12, 15)

  Guest Role
• 
  Han Ho Yong

  [Taxi driver] (Ep. 9)

  Guest Role
• 
  Go Soo Hee

  Cho Ji A [Police] (Ep. 9-14)

  Guest Role
• 
  Lee Eun Ju

  [Caregiver to Yeong Chan's mother] (Ep. 11)

  Guest Role
• 
  Yoo Ah Reum

  [Mother at Crosswalk] (Ep. 11-12)

  Guest Role
• 
  Kang Gyu Rin

  [Daughter at crosswalk] (Ep. 11-12)

  Guest Role
• 
  Park Hui Eun

  [Mi Do's mother] (Ep. 15)

  Guest Role
• 
  Han Jae Hun

  [Clothing store customer]

  Guest Role
• 
  Kim Dae Kook

  [Police]

  Guest Role

Unknown

• 
  Yang Mi Seon Unknown
• 
  Ko Tae Jin Unknown