The story was quite intriguing at the beginning with all characters in their rightful state...but at the end like almost most of the questions were left unanswered and kept us hanging.
It was a bit boring in the middle and forced me to skip little parts and the reveals were done in a very paced manner ... so, I didn't get to enjoy the reveals much...
Also there are many loopholes as mentioned by others too.
First, the setting of character of Kang Yeo joo.. She was portrayed to be so meticulous yet couldn't catch up with her husband's cheating despite so many things to suspect.
Second, NIS... The way this organization was portrayed with the higher-ups having connection with the political leaders.... Aren't they supposed to be completely independent of the political parties as this kinds of organizations handle national security matter?
Third, Kang Yeo Joo was seen framing big stories with like the tiniest evidence... Isn't that a little impractical?
The best part which I liked was Cha Soo Ho ... His every action was justified and how was unconsciously getting attracted to KYJ despite suspecting and hating her so much.