Set in the 1960’s, high school student Toru Watanabe loses his only friend Kizuki after he commits suicide. Toru, now looking for a new life, enters a university in Tokyo. By chance, Toru meets Kizuki’s ex-girlfriend Naoko in the university. They grow close because they both share the same loss. As Toru and Naoko grow even closer, Naoko’s sense of loss also grows. After Naoko’s 20th birthday, she leaves for a sanitarium in Kyoto. Watanabe, devastated by the situation, meets pure-hearted Midori during the spring semester. Midori looks like a small animal that just came into the world …

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 Christmas Day, killing 8000 people. 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.