In the future, the Japanese government captures a class of ninth-grade students and forces them to kill each other under the revolutionary "Battle Royale" act.

While hunting in the forest, Lord Asano of Ako and his samurai find a young half-breed and take him with them to live in the castle. Several years later, Lord Asano holds a tournament to welcome the Shogun to Ako. The night after the tournament, Lord Asano is bewitched into hurting Lord Kira of Nagato, and is punished into committing seppuku by the Shogun. Realizing that it was a Lord Kira's evil plot, the samurais and the half-breed sets out for revenge against the Shogun's order.