The starting and ending episodes were really good but it fell off in the middle for a bit. The female lead started to feel annoying as if she is always on mood swings, one moment she would be slapping male lead and pushing him away and next moment she'll be kissing him and throwing herself on him.
I thought it would be a full of wars kind of series but it was more of journey, it didn't bother me because I personally prefer adventure and journey kind of stories. Also I liked that there was no unnecessary deaths in this series like most of the Chinese historical dramas.
It was quite predictable, since start the way they presented certain characters scenes it was quite obvious to me that the masked man will be the villain and main lead's master will die by the end. Still it was enjoyable and the way they showed his journey was beautiful.
I thought the whole plot would be to kill the husband but the husband dies quite earlier and rest of the episodes were getting away from husband's sister and duplicate. I'm glad it was different then what I expected and there was more to the story, especially Lee Moo Seang's character stepping in as the guardian angel was my favourite part.
I really thought the wife is the murderer at the start. Why did they made her personality so chill, careless and weird in the first episode to make her look suspicious and then totally changed it in the later episodes?
It was really good kind of reminded me of Black Out. First half was quite stressful but second half was payback time. The main lead's durability was just a bit unrealistic, in every fight he'd be stabbed a dozen times but would be okay a minute later.
It was a really fun and light kdrama after a long time. Just one weird thing is how Korean and Chinese dramas cast someone real because to portray a character who is considered ugly.
K-Drama 
I'm glad it was different then what I expected and there was more to the story, especially Lee Moo Seang's character stepping in as the guardian angel was my favourite part.