This time it's war

It's three years after the events of the original Battle Royale, and Shuya Nanahara is now an internationally-known terrorist determined to bring down the government. His terrorist group, Wild Seven, stages an attack that levels several buildings in Tokyo on Christman Day, killing 8000 people. Exactly on year afterwards, the government enacts the "New Century Terrorist Counter-Measure Alternative" program, aka. the BRII act, and sends the forty-two students of Shikanotoride Junior High Class 3-B to hunt Nanahara and his cohorts down in their island stronghold. Shiori Kitano, the daughter of the late headmaster of Nanahara's Battle Royale, signs up for the program, to avenge her father. In order for the government to study the benefits of "teamwork", the new students work in pairs, with their collars electronically linked so that if one of them is killed, the other dies as well. They must kill Nanahara in three days - or die.