The storyline is superb. It contains real issue in the real world (not like time travel, reincarnation or soul shifter thingies). Bullying is happening in all level of society. It's important issue.

The acting skill of all the casts, including the young actresses and actors are excellent. With many characters, I still can keep up and remember all of them. They all are unique. Every cast was selected perfectly. The development of the characters is great. It's not only about the female lead and male lead, but also other pairing of friendship (e.g. Moon Dong Eun and her spy, Kang Hyeon Nam).

The pace or the flow of the events in the drama is brilliant. They took us smoothly from past and current, so that we understand the story.

Currently I have been rewatching, just because I like it. And can't wait for the season/part 2.