Fujibayashi Nagato was a 16th century ninja considered to be one of three "greatest" Iga jōnin, the other two being Hattori Hanzō and Momochi Sandayū. Fujibayashi's descendants wrote and edited the Bansenshukai.

Fujibayashi Nagato was a leader of the Iga ninja during the 16th century, with his followers often serving the daimyo of Oomi domain in his battles against Oda Nobunaga.

This support for his opponents would later prompt Nobunaga to invade Iga and Koga and try to stamp out the ninja clans for good, but many of them went into hiding to preserve the culture. 

Fujibayashi's family took steps to ensure that ninja lore and techniques would not die out. His descendant, Fujibayashi Yastake, compiled the Bansenshukai  (Ninja Encyclopedia).