Song Joong Ki as Kim Cheol Su
Park Bo Young as Kim Sun Yi [Teen] | Eun Joo

Supporting Cast

Lee Young Ran as Kim Sun Yi [Present]
Jang Young Nam as Yu Ok Hui [Sun Yi’s mother]
Yoo Yeon Seok as Seok Ji Tae [Sun Yi’s father’s business partner’s son]
Kim Hyang Gi as Kim Sun Ja [Sun Yi’s sister]
Yoo Seung Mok as Doctor Kang Tae Shik
Seo Dong Soo as [Colonel]
Woo Jung Kook as Mr. Jeong
Gu Bon Im as Mrs. Jeong
Nam Jung Hee as [Dong Seok’s grandmother]
Ahn Do Kyu as Dong Seok
Shin Bi as Dong Mi