I gave up on this short series and didn't see all the episodes. Here's why:
It started out promisingly, in sunny Sydney Australia where we meet the protagonist, a small time hoodlum, with this adopted family that includes a step-sister who's determined to marry him -- but she has a heart problem cuz many many Korean dramas have to have someone terminally or severely ill (which otherwise doesn't seem to affect their lifestyle). However, they return to Seoul when his long-lost real sister is spotted -- and there the story loses momentum.
One problem is too obvious: Sung Yu Ri as the long-lost sister. She's pretty -- but bland -- probably interesting only to those who are taken by her looks. She's a undead actress who walks and talks. Same goes for the second male lead, Nam Gong Min. In scenes together, they sometimes achieve a negative presence.
Yu Ri's inadequency can be seen when she appears with the cute and lively Lee Yeon Hee who plays the step-sister with the heart problem.
Amiable Gong Yoo does well as the brother -- but the role isn't as demanding as the one in the superior series COFFEE PRINCE -- which is my way of saying the scriptwriting doesn't compare, either.
At least, there's nice photography and location shooting.
If you obsessed with any of the actors, you might get more enjoyment out of this than I did.