Years of civil war have brought the ninjitsu code and its warriors to the brink of extinction. A ninjitsu master selects three children to carry on the ninja traditions for the next generation: two brothers, Kazuma and Sho, and his own daughter Aya. He begins to train them.
Fifteen years pass. The oldest boy, Kazuma, begins to reject all the ninjitsu teachings, save the technique of strength. Obsessed with power, Kazuma demands that the master teach him the ultimate technique. The master refuses, and Kazuma vows to return one day and take revenge. Sho and Aya continue their studies and master the ninjitsu teachings.
Kazuma returns with an army and the resources to build a fortress. Although the old master has died, his pupils contain the secrets of the ultimate technique. Kazuma sets up a trap to lure Sho into his hideout, and kidnaps Aya to use her as a bait.
In the ending, Kazuma sacrifices himself to save Aya and Sho from an explosion.
Shinobi X