First, I hesitated to watch the Drama, because at first I didn't like the story. But now I have to say, that I would had been regret it. Story: Like I said, I didn't like the story at first, but after I watched a few episodes the story got better and better. In my opiniont the story grows more and more from episode to episode until the end. Honestly I liked the 2nd half more than the first half. Acting: I watched the drama because of Hwang Jungeum and Park Seojoon. Both of them are very good actors. Their chemistry as siblings in 'Kill me, Heal me' was excellent. So I began watching this drama and was excited to see their chemistry as Ex-Classmates. HJE is an ecxellent actress. I learned to know her, when I watched 'Secret'. She is so emotional that I can't name many other actresses like her. Her role was at the beginning (for me) a little annoying. Sometimes I thought "How dumb can she be?". But I liked how her role grows in the drama, so in the end I like Kim Hyejin. PSJ played Seongjun and I liked him. My first drama wirh him (Which I have finished) was 'Kill me, Heal me' and if Ji Sung hadn't played his role so perfect I had loved him even more (Maybe a second Lead crush^^). But now he was the first Lead and I think it was a better role than in KMHM for him. Go Junhee acted really well, but her role was annoying. I didn't like her and every time I saw her, I was like 'Oh no, why is she so bad?' And Choi Siwon was good, too. Normally, I don't like many Idols who act, but some of the can act. In my opinion Siwon is an Idol who can act better than he can sing. His role was funny and I think, that he could play a funny and crazy role better than a serious person. The best was "Jackson"^^. I laughed really often. Then ther were two other actors whom I liked. Park Yoohwan and Shin Hyesun. Both of them were so cute. Music: The music suits the theme of the drama and I like it. The song from Siwon was the best, I think. But the drama as other amazing OST. If I have time in the future and no other dramas to watch (But I doubt it) I would watch this drama again.