Romance is a Bonus Book: The Casts
- Kang Dan-i (37 years old) played by Lee Na-young
A new divorcee and former advertising copywriter. Cha Eun-ho’s best friend since childhood. She later joins the publishing company as a temporary task support team member.
- Cha Eun-ho (32 years old) played by Lee Jong-suk
He’s the youngest editor-in-chief in the publishing company and a successful writer who is also Kang Dan-i’s long time friend. He has been harboring romantic feelings for her since they were young.
- Song Hae-rin (29 years old) played by Jung Yoo-jin
Kang Dan’is supervisor as he is the Lead Content Development Editor and trainer of the recruits. She has an unrequited love for Cha Eun-ho.
- Ji Seo-joon (29 years old) played by Wi Ha-joon
A freelance book designer, the publishing company, is looking to hire. After he met Kang Dan-i, he started to develop feelings for her.
- CEO Kim Jae-min played by Kim Tae-woo
A bit over-eager but an overall well-meaning boss of a publishing company where Cha Eun-ho works.
- Director Go Yoo-sun played by Kim Yoo-mi
Kang Dan-i’s former cold-hearted boss who discourages her efforts becoming a part of the marketing team and only gives her menial tasks around the office.