Somehow managed to not see this until today.
Overall, I thought it was fairly entertaining piece of fluff. The acting was about standard for an Asian film full of Japanese teenagers - lots of melodrama, suicidal ideation and the obligatory unspoken loves with tragic ends.
On the plus side.... hysterical Jap schoolgirls with semi-automatic weaponry!
I think some of the sub-plots/character motivations get lost in the translation (although crappy screenplay is just as guilty), but I frequently found myself chortling to the miserable fortunes of the kids.