I was not a fan of Nam Joo Hyuk but I did watched majority of his work. I could say he 100% shined on this series. His acting and chemistry with Kim Tae Ri was unexpected and surprisingly good.
The rest of the casting was also great. They have their moments that makes the series enjoyable.
But aside from the actors, what's separate this is the storytelling - we have been here before with series that shows flash forwards that will make you guess - but, finding out who is Kim Min Chae and how was everyone is present is the by far the hardest. It all very intricate and intriguing.
It very well capture the growth of the characters in a time where; people grow based on real life experience, by being out their and experiencing the growing pains and transition of being teenagers to adult.