This drama turned out to be completely unexpected. I thought it was going to be an light-hearted but insightful drama about the difficulties and the stress that Japanese students have to overcome during their high school entrance exams (still, elements that were portrayed in the drama), but it turned out to be more of a thriller/mystery kinda drama. At first I wasn't really sure I was going to keep watching it, but the second episode totally got me into the storyline. I loved this drama! I loved it so much that I watched it with Japanese subtitles (because I couldn't wait for the English ones) and re-watched all the episodes out when it wasn't even finished. I think this was the revelation drama of this season (at least, for me).
Even though the rhythm was quite slow (like 10+ episodes for a few hours) I didn't feel bored the slightest. I was surprised this drama focused more on the teacher side instead of the student side, since it was about high school entrance exams, but it was really interesting. The mystery element was nicely used and there were lots of turns of events that kept the viewer watching to find out the truth behind all the happenings.
All in all this was a totally unexpected and really good drama, and I wouldn't mind re-watching it, which I think I'm going to.