The plot seemed strange to me in the beginning and the production of the film didn't look like it has a lot of quality; however, when I see how those kids behave at the beginning of the story, I was like...well, they deserve to be locked up and learned some lessons. I decided to watch the series, and it was the right decision!
The story is very interesting. It keeps us guessing what is in the head of Hiragi the teacher. As the story unfolds, I found that the film meant to discuss deeper subjects that drive problems inside these students and we see them forced to admit their own fault and learn from it. All along the way, the people in social media are shown criticizing everything, making fun with the situation, judging, blaming, and saying all terrible things through their comments. In the end, we find out that this is lesson for those social media users. They are the real killer and they, too, should be ashamed.
The performance of the cast overall was very good. The acting of the actor who plays Hiragi was very outstanding, deserving award. The CG and the effects were average but it is passable. The plot is very unique and we can't guess the ending. It has its exciting moments with twist and turn.
But I want to re-emphasize here that the best thing about this series is the important messages it is speaking to the audience in a powerful way. It is an important message and I respect the director, writer, and production team for producing this series. It doesn't look as good as Hollywood work, but it is more precious.