The main theme is 'Guilt can be an obstacle if you cannot manage to forgive yourself'.
This theme is executed and we all felt it, but in the end the drama was really boring for me.Company politics felt like a filler, still, it wasn't enough to fill 16 episodes.
Should have been a movie.
As for the acting, the female lead's way of thanking even became really annoying as the drama neared ending, I didn't enjoy her acting at all. The male lead, a.k.a. Blue Bird, reminded me the Big Bird of Sesame Street, the cuteness was overacted and became funny-and not in a good way.

The best two things of the drama was, Re Lee's phenomenal acting- she played the part of 17 year old Ha-ni; and the morning company dance, which I found hilarious, brilliant and uplifting all at the same time.
Can't say that I recommend this.