Begins Youth

Director

• 
  Kim Jae Hong

Screenwriter

• 
  Kim Soo Jin
• 
  Choi Woo Joo

Main Role

• 
  Seo Ji Hoon

  Kim Hwan | Kim Chang Jun [Young]

  Main Role
• 
  Noh Jong Hyun

  Min Ce In

  Main Role
• 
  Ahn Ji Ho

  Jeong Ho Su

  Main Role
• 
  Seo Young Joo

  Kim Do Geon

  Main Role
• 
  Kim Yoon Woo

  Park Ha Ru

  Main Role
• 
  Jung Woo Jin

  Kim Joo An

  Main Role
• 
  Jeon Jin Seo

  Jeon Jae Ha

  Main Role

Support Role

• 
  Jung Sung Il

  Kim Chang Jun [Kim Hwan's father]

  Support Role
• 
  Kim Nam Hee

  Song Jun Ho [Chang Jun's secretary]

  Support Role
• 
  Nam Myeong Ryeol

  Koo Hyun Bok [Principal]

  Support Role
• 
  Woo Hee Jin

  Hwang Seo Yoon [Jae Ha's mother]

  Support Role
• 
  Sung Ji Ru

  [Homeroom teacher]

  Support Role
• 
  Kim Young Woong

  Kim Seong Hoon [Joo An's father]

  Support Role
• 
  Lee Hang Na

  Shim Seon Mi [Ha Ru's mother]

  Support Role
• 
  Yeo Woon

  Choi Ji Han [Psychiatric patient]

  Support Role
• 
  Im Chul Hyung

  Seo Sung Tae [Jae Ha's step-father]

  Support Role
• 
  Park Ji Hoon

  Seo Min Kook [Jae Ha's step-brother]

  Support Role
• 
  Lee Do Yeop

  Min Young Ho [Ce In's father]

  Support Role

Guest Role

• 
  Moon Jong Ho

  [Student] (Ep. 1)

  Guest Role
• 
  Kim Gye Seon

  Kim Jung Hee [Ho Su's aunt] (Ep. 1-2, 5, 8, 10)

  Guest Role
• 
  Cha Soo Rin

  Mrs. Jeong [Do Geon's homeroom teacher] (Ep. 1-3)

  Guest Role
• 
  Yoon Jung Sub

  [Teacher] (Ep. 1-2)

  Guest Role
• 
  Jeon Young

  [Housekeeper] (Ep. 1, 3, 10)

  Guest Role
• 
  Park Young Soo

  [Container owner] (Ep. 1, 5, 8-9)

  Guest Role
• 
  Chae Yeon Hee

  [Saleswoman] (Ep. 2)

  Guest Role
• 
  Nam Da Nu

  [Thief student] (Ep. 2)

  Guest Role
• 
  Kim Ji Hoon

  Jeong Ho Su [Child] (Ep. 2, 8)

  Guest Role
• 
  Han Yun Jun

  Min Ce In [Young] (Ep. 2, 4, 7-8, 12)

  Guest Role
• 
  Cha Yu Jin

  Kim Eun Ju [Ce In's mother] (Ep. 2, 4, 6-8, 12)

  Guest Role
• 
  Nam Jin Bok

  Park Noh Ah (Ep. 3, 5, 8-10)

  Guest Role
• 
  Jung Hyun Joon

  Park Ha Ru [Young] (Ep. 3, 5, 8-10)

  Guest Role
• 
  Kim Bi Bi

  [Psychiatrist] (Ep. 3, 10, 12)

  Guest Role
• 
  Kim Tae Yul

  [Captive kid] (Ep. 3, 5, 8-10)

  Guest Role
• 
  Jang Joon Ho

  [Doctor] (Ep. 4)

  Guest Role
• 
  Lee Yoon Jae

  Byeon Won Joong (Ep. 4-5)

  Guest Role
• 
  Choi Seung Hoon

  Kim Joo An [Young] (Ep. 4, 10, 12)

  Guest Role
• 
  Shin Bo Ra

  Kim Eun Hye [Joo An's sister] (Ep. 4, 6, 12)

  Guest Role
• 
  Won Chun Gyu

  [Police officer] (Ep. 5)

  Guest Role
• 
  Kim In Kwon

  [Police officer] (Ep. 5)

  Guest Role
• 
  Park Ah Sung

  Kim Do Hyun [Do Geon's brother] (Ep. 5-7)

  Guest Role
• 
  Kang Tae Ju

  Park Sang Min [Ha Ru's brother] (Ep. 6)

  Guest Role
• 
  Kwak Na Yeon

  [Ha Ru's neighbor] (Ep. 6)

  Guest Role
• 
  Lee Shi Hoo

  [Thug] (Ep. 6-7, 10, 12)

  Guest Role
• 
  Park Yong

  Seo Jang Won [Chang Jun's party attendee] (Ep. 7)

  Guest Role
• 
  Park Gi Seon

  [Churchgoer] (Ep. 7)

  Guest Role
• 
  Jang Eui Don

  [Chang Jun's party attendee] (Ep. 7)

  Guest Role
• 
  Kim Jae Heum

  [Chang Jun's party attendee] (Ep. 7)

  Guest Role
• 
  Kim Yoon Ho

  Jeong Mi [Student] (Ep. 8)

  Guest Role
• 
  Jung Hyun Chul

  [Teacher] (Ep. 8-10)

  Guest Role
• 
  Won Yun Seo

  Kim Eun Hye [Young] (Ep. 9)

  Guest Role
• 
  Park Jung Eon

  [Doctor] (Ep. 9)

  Guest Role
• 
  Byun Yoon Jeong

  [Detective] (Ep. 9)

  Guest Role
• 
  Shin Min Soo

  [Protester] (Ep. 10)

  Guest Role
• 
  Kim Yong Jin

  [Chang Jun's man] (Ep. 10)

  Guest Role
• 
  Kim Mi Seung

  [Nurse] (Ep. 10-12)

  Guest Role
• 
  Jo Seung Yeon

  Lee Young Ran [Joo An's mother] (Ep. 10, 12)

  Guest Role
• 
  Jeong Soo Hyun

  [Thug] (Ep. 10, 12)

  Guest Role
• 
  Ki Eun Yoo

  Kim Hwan [Child] (Ep. 11)

  Guest Role
• 
  Lee Jae Hak

  [Bully kid] (Ep. 12)

  Guest Role
• 
  Park Ok Chool

  [Do Geon's aunt] (Ep. 12)

  Guest Role
• 
  Kim Nak Gyun

  [Do Geon's boss] (Ep. 12)

  Guest Role
• 
  Lee Seung Hyung

  Park Jin Wook [Ha Ru's father]

  Guest Role
• 
  Oh Mi Hee

  Song Nan Young [Do Geon's mother]

  Guest Role