I read a review under another drama stating that often the issue with kdramas is that they tend to be complicated just for the sake of being complicated, and that's exactly the case. I wish I had watched only the last 5 episodes. Boring and slow at the beginning, just the acting of Lee Jun Ho and Lee Se Young kept me from dropping. I started to enjoy the show as soon as they stopped adding more and more characters and intrigues.
In the end I felt like nothing was resolved (but actually it was, it's just me that couldn't thoroughly follow all the scheming and plot twisting) but the story left us with a bittersweet ending which wasn't completely sad in my opinion.