The two leads created the most depressing characters I have ever seen. I don't think either of them smiled until the end of the last episode. I was smiling then, too, because I didn't have to watch any more of this. I hadn't realized it was only 12 episodes, so I'd decided to drop it. The music was unremarkable, although the finale song was nice.
I suppose the point of this is to shed some light on the abuse of trainees, especially sexual favors demanded. It's a retelling of the tragedy of Sunny, Jang Ja-yeon. If you are new to K-drama, look her up on Wikipedia. As such, this show brought no new insight, and it's a retelling of something that happened 12 years ago. It offers no solutions or productive actions. Between the borrowed (stolen) plot, dismal performances and so-so music, this isn't worth your time. It certainly wasn't worth mine, and if there had been much else to watch while this was running, I wouldn't have bothered.