First and foremost, how the hell do you able to mess up such a beautiful idea like this? The idea for this drama is really good, but yet the writer decided to screw it up. This drama should be ended in episode 12, even 8! The third time travel was uneccessary. Also the serial killer idea is really awful. Out of 9 million citizens of Seoul, why did the serial killer had to keep choosing Sol IN ALL OF THE TIMEFRAME? The serial killer in the third time travel already feels unecessary because Sol had dodged it in the second time travel, but maybe they needed it because he killed Sun-Jae in the present. Yet the serial killer should not even show up in the present after the fourth time travel, because the timeframe had been changed! Those two premises are there just only to support the ending that the writer's intended, nothing more. This drama might be too long that they had to add ridiculous things such as the second watch, that one is horrendous! I understand that most K-Dramas has strong start and hollow ending, but I really did not expect this one became silly only after half of the season.

On the contrary, thanks to Hye Yoon, Woo Seok and Geon Hee who played their characters excellently, they literally carried this drama. Overall, this drama is still enjoyable since it brings a lot of morale of the story, but you may get frustrated after watching several episodes.