I think it captured the high school feeling of despair better than any other movie. The high school movies I am used to usually transform everything into a battle between characters where in the end the good guy wins. Or maybe he loses. But what if you don't want a battle? What if you just don't know what to do or you just don't care?
In Aoi Haru a deadly game decides who the leader of the school will be. A lonely quiet guy wins the game, but he does it only because he doesn't care enough to fear for his life. He actually does it for the game, not for the leadership. That annoys the hell out of his friend, ex boss himself, who can't understand someone that does not want to abuse his power. In the end their friendship is brutally ended.
There are some interesting metaphors in there, like the flowers that the boys are trying to grow, even if just one of them lives to see them blossom. It is also interesting that it is a boys only high school, maybe that's the norm in Japan, I don't know.
There is also in the movie the hidden message that neglect and inaction can do more damage than acting badly. I am talking here about the teachers in the film, that are just dictating machines with no will to educate or care. I mean, doctors can be accused of malpraxis. Lawyers, too. Yet teachers, who are supposed to create social beings from adolescents, are not held responsible for their mistakes.
Enough babble. This is a good film, maybe a bit long, but it does need almost every scene. The soundtrack is also very nice and fits the plot. It is worth watching.