From the introduction:
The shinobi world had its origins when the Five Great Nations relied on vast armies of samurai and archers for their military and protection. However, with the samurai came the greedy Shogun who used their military as their own personal armies rather than as national armies. Though the great nations balked against the Samurai’s audacity there was little that could be done. Eventually, however, groups of men and women who were trained in the ways of manipulating and controlling energy both within and without the body, as well as silent and deadly martial warfare, began to formulate together into large family groupings, called Clans. These Clans developed techniques through the manipulation of the energy called chakra, which resides in all living beings, and they kept the most advanced and secretive techniques only to themselves. Some of these techniques would alter the physiology of a being, others were simply different methods of employing ones chakra, and others still formed bonds with the creatures of nature. Regardless, these techniques would earn the name of Jutsu.