My favorite Kdrama ever. I'll never get over it and I'll probably rewatch (the scenes between the ML and FL) several times a year.

Full disclosure: I watch Kdramas for the romance, and the romance here is TOP NOTCH. The background story for this one is fine. It makes sense and as an action plot device is pretty good. Most of the time, the background story helped add tension to the romance, so I only fast-forwarded through the action plot scenes during the last 4 episodes when I finally got tired of them and felt like they weren't adding to the romance. (Usually, I'm fast-forwarding through the non-romance scenes starting with episode 3).