Its simple really

Kids pissed off over BR act (BR act is a law were everyyear a class of school kids are kidnaped and forced to kill each other off on a remote island, if they refuse the bombs straped to thier necks blow up.)

Nanahara was chosen for the BR act and was the survivour, but now wanted as a murderer he forms "The Wild Seven" Terrorist org determind to kill the adults that did this to him. He was responcible for the tokyo bombings that killed 8,000 people at christmas.

But don't forget, its just a film. That I thought was very cool.