At first, everything is perfect: action, suspense, romance, drama! the acting is absolutely amazing and the first episode is one of the best first episodes of all time!

but from half to the end, it seems that the writers get lazy and the episodes are dragged on. the awful cherry on top was the ending.
not only it's an open ending (with no sequel) but it's also a TERRIBLE ENDING. really out of character put the two mains in that situation, it makes NO SENSE.

I struggled a bit to finish and was really disappointed with the end. But, because the first part was a masterpiece I can't bring myself to give a lower rating. also they have Bae Suzy so it's a plus lol