Interesting.
I am a huge fan of Battle Royale. I own both of the special edition movies, (even though BR sucked nards) all of the comics, soundtracks and the book. I will probably even go out to see the American remake, even though I am having major doubts about it.
I have to say that you didn't do a bad job, but everything seemed a bit slow in comparison. When the characters are running, it did not have the same feel of anxiety when someone is getting chased like in the movies/manga/book. However that is probably just a personal issue.
The South Park designs are ok.. though not prefered. Watching them hop around while they are running, made me lose interest.
With these qualms aside (since most of them are probably stemming from my fangirlism) it's not bad. I loved how you put the classical music from the movies in the flash and it had a little bit of an authentic feel.