It's the near future, and apparently kids in Japan have become rude and disrespectful, so the adults decide to teach them a lesson by randomly kidnapping a 9th grade class each year and forcing them to fight to the death on some remote island.
The great thing about this is the action and gore, which prompted some glowing comments from Tarantino on the dvd cover. There's lots of clever deaths (see the decapitated head with the grenade in the mouth below), particularly of the Tarantino kind where roomfuls of people are all blasting away with blood flying everywhere.
However, I can't go beyond 3 stars because the story just didn't work for me. For instance, how is a death battle going to teach kids a lesson if the adults KEEP IT A SECRET? It's apparently been going on for a few years by the time the kids in the film get drafted, but they have no idea what's going on. So yeah, it's almost like the director is just saying: "Screw context. I'll give you a nod with this lazy story about juvenile delinquents, but I really just want to get right to the gore." I think I'd have preferred he just skip context altogether.
There's also the problem that the deaths come so fast that you never really know or care who's being wiped out--it's like the early days of Survivor! I think they start with 42 students, and within not much more than an hour, it's whittled down to 3, so yeah, blink and someone's gone.
A lot of the character development also gets tiresome as it plays on what I guess we could call "Asian-girl romance" themes. It seems like every girl's death somehow evokes wistful musings about one of the boys in the class. I know there's a whole genre of manga dedicated to these flirtations, and I think we see some bleed-in from that genre here. Sort of like Hunger Games in that as well, actually.
Anyway, some good gore and action, but kinda vacant overall so that my mind was wandering a lot.