From the Introduction:
Capable of defeating hordes of enemies on his own, a lone ninja—when given sufficient reason—can bring an evil emperor’s dynasty to its knees. Unfortunately, you’re not that lone ninja. Your evil empire is about to fall apart. You’ll be up against overwhelming odds: your entire ninja army versus a single hero. Are you up to the challenge?
Conservation of Ninjutsu is a single-player role-playing game in which you, the evil emperor, must rally his ninja army to defeat a lone hero who threatens your way of life. The hero fights for good, justice, and fair taxes. Will you let him ruin your dynasty, or will your ninja hordes be strong enough to stop him?