Even if the rating is Zero I will still watch because of Shin Sung Rok, a great actor! Always watched him as a second lead or a supporting character, in this, he is the main lead, can't miss this opportunity + Thriller, so will watch.
My only observation was, in the initial episodes while showing the houses of North Korean, they used to show the North Korean leader pictures in those houses, slowly after the 8th or 9th episode the pictures showed looked a little faded or blurred, but it was good drama, I liked both the lifestyle North Korean people lifestyle, like storing the food items and no internet more of physical activity, as well I liked South Korean up-to-date technology side. I thoroughly enjoyed the comedy of the drama, more than the main leads I loved all the other characters a lot, complete fun package.
EP-13 has a logic issue, no police will proceed further without securing the witness, I can see there is a logic issue, which can extend the episode, just because of that I m accepting if at all there is best twist for this wrong logic it will be mind-blowing. The next coming episodes should properly justify it.
Beautiful screenplay, Finished in one sitting, True feeling of each character is exposed or bought into the play, Kamio Fuju has a bright future. I usually don't watch the age gap, adultery/ extramarital affairs series, or movie, but this fall into very much righteous in spite of the age gap. It is not practically possible, maybe that's the reason director left it as open-ending. But it is worth watching.
episode by episode expectation increases and it is damn interesting to see the development, BGM is also so good, tvN is always best, Both male and female leads are excellent, didn't expect that I would fall this much into its story/Drama. Thoroughly enjoying...............
Studio Dragon never disappoints. Interesting story. Quite a work would have happened in Post-production, even minute information of a scene is also well filmed. Kim Soo Hyun became size zero! First time I like Seo Ye Ji. Perfect for the character. After the crash landing on you, this is my favorite drama now. :)
"Marry me or not" is one of the best, Roy and Alice pretty couple, damn good chemistry. Modern woman concept, I liked it. I don't how many times I have watched MARS, Almost forgot "Behind your smile" was also good.
K-Drama 
Liu Yi Junis also a good actor.