I randomly chose to watch this as I didn't want to watch romcom or fantasy also needed drama with less episode. And here is the review
1. I watched with no expectation but I loved the whole drama pace and plot.
2. They will surprise you and you'll crave for next episode.
3. They maintain the pace without getting more complicated.
4. As story is about the time travel, they don't confuse you much or say you'll not be frustrated and go with the storyline.
5. Actors are brilliant and lead character's chemistry is on top notch as it is not a romance drama, you can only crave for them to be together in any other drama.
6. Less osts but, are melodious.
7. Only 12 episodes if you don't wanna watch 16 episodes drama.
8. Somethings are not explained but they don't cause much affect on story.
Just go for it , you will love it.