I love the overall plot, but for me, the chemistry between the two main leads was kinda off. I cant really feel it, even awkward in certain scene. BUTT dont worry yall they have some side stories that's really interesting to watch especially the story abt the relationship between two brothers. the character development of the two villains was just really great and that made me fell for them more than i should do. Lee Rang was really such a scene stealer and his character development was a really great and heartwarming touch of the drama. He may seem like a jerk but if you see deeper you'll fall for him more than you do to the main leads and that's what happened to me lol.
I cant say it had a happy ending nor sad it really all depends on you but for me it was not a happy ending. I still remember how i cried SO hard throughout the last episode omg even if i rewatched the clip now id still cry TT

p.s. I really wish Kim Bum gets to be the main male lead in another drama. his acting was really amazing it was such a waste of talent that he never be one in any drama so far.