The plot is great, the way the told the past while showing the present just shows how well it was written and directed.
The choice of casting couldn't've been better, they really made us connect with the characters and their storyline. We feel empathy towards the people we deem as" bad guys" because they show us that in the end we are all humans and sometimes we are just pawns in something that doesn't need to exist. Each character was shown their story, not a second too long nor too short. And it was a happy ending ;)
Overall, amazing kdrama that I will definitely rewatch in the future.