Romance Is a Bonus Book cast is including:
Lee Jong-suk as Cha Eun-Ho (16 episodes), Lee Na-young as Kang Dan-Yi (16 episodes), Jung Eu-gene as Song Hae-Rin (16 episodes), Wi Ha-jun as Ji Seo-Joon (16 episodes), Kim Tae-woo as Kim Jae-Min (16 episodes), Kim Yu-mi as Ko Yoo-Sun (16 episodes), Kim Sun-young as Seo Young-A (16 episodes), Jo Han-chul as Bong Ji-Hong (16 episodes), Kang Ki-doong as Park Hoon (16 episodes), Park Gyu-young as Oh Ji-Yool (16 episodes), Oh Eui-sik as Hong Dong-Min (16 episodes), Choi Eun-kyeong as Ji-Yool's mother (16 episodes)