This is one of the better k-dramas since it's not as cliche, has great music, and eye candy... So JiSub and Seo InGuk.
The storyline is fun at first, but makes for a very confusing relationship. The 2 leads speak to each other in cryptic dialog about it, making it hard to follow (especially for a non-Korean who doesn't get the references to mentioned manhwa and concepts like "candy girls"). It's so frustrating how they communicate, and I hated the stupid decisions they made because they are immature.
Also the FL is supposedly so smart and talented, but we never see a shred of evidence. She is always running head first towards danger and acting like a fool.
It's worth watching, that being said. But anyone watching with subtitles may need to pause to reread the scenes in which they argue to fully understand. Even then you may get lost around episode 12 or 13.