To be fair, this show is probably for people who may like (guess only) kdrama shows similar to : Miraculous Brothers, Longing for you, Flowers of Evil,. Kidnapping Day, Let's get grab by the Collar.
Structure wise, it's not tight at all. First episode is solid. Then all seems to be on autopilot and went downhill with over the top melodrama, empty threats and rhetorical questions.
A classic innocent man story, that adds characters half way through the story ... and then some. To me that's cheating. The conspiracy seems all too obvious and yet overwhelmingly ..... what's the word..... ridiculous.
Just way too thin, substance that is. So thin that there's constant flashy backs and plot replays/reminders at episode beginnings. I just finished The Frog and so much more unique, creative and well written on all fronts : characters, plot, timeline and meaning.
Thin, when compare to (plot, execution, direction) other kdramas the likes of Somebody, Beyond Evil, Mask girl, Shadow Detective, Mouse, A shop for Killers, A Killer Paradox.
Overall, it's a melodrama disguised as a thriller.
Only saving grace is acting, that's it.