Phew, that was a quick read. I'm fine with the ending. Would've liked it anyway, even if it was super dark. I came for the survival game.
Overall a huge mixed bag. Great art and action, even if it required a bit suspension of disbelief to enjoy it fully. I could stomach 14/15 year old students looking like in their 20's or 30's, Mitsuko in high heels running and jumping around, even the ki blast stuff, but Kiriyama was too much, for too long, to the point where it became hilarious. Some of the other characters were funny as well in a twisted way. However, it was always in line with the portrayal and within reason(minus the facial expressions at times xD) I liked almost all of the backstories btw. Same goes for the different ways of how the students were coping with the extreme situation. There was cheesiness, often more than necessary, but most of the time I vibed with it.
Most importantly, it was never dull with all the crazy stuff happening. That made up for the lack of emotional connection.