I watched this while the drama aired, then watched it 6 more times. First of all, I have to praise the acting, each person did their job with a clean 10. The storytelling is incredibly good, but confusing for some people, to understand the drama people need to think about (I have no intention of valuing but anyone who says drama is bad because you are not ready to understand the action) ... The music is perfect. from OST to sound effects, every moment kept me on the brink of uncertainty. If you are a smart person, who likes psycho drama and a person who loves the open ending, you MUST watch this!