A young man decides one day to start killing yakuza. After he kills his first two he gets roped into helping a wannabe gangster and his bumbling underlings to perform a hit. While things work out in the beginning, this young psychopath quickly becomes more trouble than the gang expected. Will they be able to rid themselves of him, or will they be his next victims?

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.

When he returns to Earth to attend the wedding of his friend in Saipan, Musashi meets a beautiful girl named Shau who claims to come from the bottom of the sea. Just then, Monster Scorpis reappears in the sky above the island and Musashi faces the monster in order to protect the girl. What is the girl's true form? And what is the strange shadowy form that follows the monster Scorpis?