Romance Is a Bonus Book

Composer

• 
  Nam Hye Seung
• 
  Park Sang Hee

Director

• 
  Lee Jeong Hyo

Screenwriter

• 
  Jung Hyun Jung

Main Role

• 
  Lee Na Young

  Kang Dan I

  Main Role
• 
  Lee Jong Suk

  Cha Eun Ho

  Main Role
• 
  Jung Eugene

  Song Hae Rin

  Main Role
• 
  Wi Ha Joon

  Ji Seo Joon

  Main Role

Support Role

• 
  Kim Tae Woo

  CEO Kim Jae Min [Gyeoroo president]

  Support Role
• 
  Kim Yoo Mi

  Go Yoo Sun [Gyeoroo director]

  Support Role
• 
  Jo Han Chul

  Bong Ji Hong [Editorial team]

  Support Role
• 
  Kim Sun Young

  Seo Young Ah [Marketing team team leader]

  Support Role
• 
  Kang Gi Doong

  Park Hoon [Marketing team]

  Support Role
• 
  Park Gyu Young

  O Ji Yul [Editorial team]

  Support Role
• 
  Lee Kwan Hoon

  Lee Seung Jin [Marketing team]

  Support Role
• 
  Choi Seung Yoon

  Bae Kwang Soo [Marketing team]

  Support Role
• 
  Oh Eui Shik

  Hong Dong Min [Dan I's ex-husband]

  Support Role
• 
  Lee Ji Won

  Hong Jae Hee [Dan Yi & Dong Min's daughter]

  Support Role
• 
  Choi Da In

  Kang Dan Yi [Young]

  Support Role
• 
  Jo Deok Hee

  [Clerical worker]

  Support Role
• 
  Lee Seo Hwan

  [Hae Rin's father]

  Support Role
• 
  Lee Ji Ha

  [Hae Rin's mother]

  Support Role
• 
  Yi Chae Woon

  Chae Song Yi [Editorial team]

  Support Role
• 
  Han Seung Hyun

  [Logistics center staff]

  Support Role

Guest Role

• 
  Cha Soon Bae

  [Drunk man] (Ep. 1)

  Guest Role
• 
  Shin Hye Jung

  [Eun Ho's ex-girlfriend] (Ep. 1)

  Guest Role
• 
  Kim Ji Hyun

  [Interviewer] (Ep. 1, 3, 11-12)

  Guest Role
• 
  Park Yoo Rim

  Eun Jung (Ep. 2)

  Guest Role
• 
  Kim Kang Hoon

  Cha Eun Ho [Young] (Ep. 2)

  Guest Role
• 
  Noh Jong Hyun

  [Ji Yul's boyfriend] (Ep. 2-3)

  Guest Role
• 
  Hwang Se On

  Kim Na Kyung [Eun Ho's ex-girlfriend] (Ep. 2, 5)

  Guest Role
• 
  Lee Do Hyun

  Mr. Park [Writer] (Ep. 5)

  Guest Role
• 
  Yoon In Jo

  [Yoo Sun's friend] (Ep. 5)

  Guest Role
• 
  Choi Ga In

  [Yoo Sun's friend] (Ep. 5)

  Guest Role
• 
  Kim Nan Joo

  [Yoo Sun's friend] (Ep. 5)

  Guest Role
• 
  Choi Jung Hoon

  [Street Busker] (Ep. 5)

  Guest Role
• 
  Kim Do Hyung

  [Street Busker] (Ep. 5)

  Guest Role
• 
  Geum Bo

  [Blind date man] (Ep. 6)

  Guest Role
• 
  Park Seung Tae

  Yoo Myung Sook [Novelist] (Ep. 7, 11-12)

  Guest Role
• 
  Lee Kyung Wook

  [Ji Yul's mother's secretary] (Ep. 7-8, 14)

  Guest Role
• 
  Choi Eun Kyung

  [Ji Yul's mother] (Ep. 7, 9, 11-12, 14)

  Guest Role
• 
  Oh Kyung Joo

  Kim Myung Soo [Blind date man] (Ep. 12)

  Guest Role
• 
  Song Young Jae

  Nam Won Suk [Pureunmaeum Book Publishing president] (Ep. 14-16)

  Guest Role
• 
  Lee Kang Wook

  Park Jung Shik

  Guest Role
• 
  Yang Seung Kul

  Choi Hyung Su [Writer]

  Guest Role
• 
  Lee Ho Jae

  Kang Byung Jun [Writer]

  Guest Role
• 
  Park Sang Wook

  Ahn Jung Hoon [Yoo Sun's ex-fiance]

  Guest Role
• 
  Jo Jung Chi

  [Guitarist]

  Guest Role
• 
  Cho Yu Ha

  Seo Hyeon [Jae Min's daughter]

  Guest Role
• 
  Lee Jong Goo

  [Byung Jun's doctor]

  Guest Role
• 
  Kim Esther

  [High school student]

  Guest Role
• 
  Kim Mi Hye

  [Jewelry store employee]

  Guest Role
• 
  Park Jin Soo

  [Female university student]

  Guest Role
• 
  Kim Kyung Il

  [Bookstore employee]

  Guest Role
• 
  Baek Chun Ki

  [Marketing dept. chief]

  Guest Role

Unknown

• 
  Moon Joo Yeon Unknown
• 
  Lim Dong Yoon Unknown
• 
  Lee Ji Hae Unknown
• 
  Hong Boo Hyang Unknown
• 
  Choi Yoo Jin Unknown
• 
  Shin Yeon Mi Unknown
• 
  Im U Hyeon Unknown