I felt the only two letdowns of this drama would be
1. the female lead's character like , omg why they had to show her that irritating. At one point, u just feel annoyed and in fact I liked the girl who was kangchul s best friend. She suited with ljs, def could have done better with him. Tbh, Its more of the overacting of the actor for me than the character features.
2. After 10th episode's screenplay. The whole kang chul forgot and regained memories was unnecessary and it has become like a must in every kdrama I feel. I cannot remember what happened after the 10th episode but they could have done it really better.
Other than this, its a pretty good drama, you can't help but fell In love with Lee jong suk, again he is an absolute treat to watch . even tho the female lead is annoying, their chemistry was amazing. As always , jongsuk has good chemistry with everyone he works with. The side characters are great too. So, yeah that's pretty much it.