The Kishū-Ryū was a comprehensive samurai school of martial arts and espionage, based on the Kusunoki Gungaku (Japanese arts of war), and not just shinobi no jutsu alone. It was founded by Natori Masatake and his book, the Shoninki (True Shinobi Account), was a transmission of Kishū-Ryū shinobi arts. It is said to have originated from the descendants of Iga after the Iga-mono were annihilated by Oda Nobunaga. Before Natori Masatake, the Natori clan followed the Koshū-Ryū Gunpo school of military affairs.
Natori Masatake's grandfather, Natori Masatoshi, fought as a Takeda samurai and when he retired he joined the clan he studied from, the Sanada clan. Masatoshi's son, Natori Masatomi, carried on the Natori family for him and joined the Tokugawa clan, a house which was directly related to the shogun. The Natori family broke off into two divisions, the Tokyo Natori and the Natori in Kishu.