Let us look at the life of the ninja.
In peacetime, they were devoted to farming.
According to the "Iran-ki" written by Kikuoka Nyogen of Iga, "In the morning they devoted themselves to their family business, and in the afternoon they would gather at a temple to practice military arts and the way of war".
When the time came to fight, bells would ring in the village, and everyone from the farmers to the monks were expected to stand up with their best weapons.
In addition to agriculture, a variety of livelihoods sprouted in the area.
In the Nara period (710-794), the Igasoma and Kogasoma mountains, which supplied lumber for the construction of the Todaiji Temple, were opened, and lumberjacks cut large trees and jumped from tree to tree to produce lumber.
Mountain religion flourished in the mountains, and mountain priests trained themselves severely on the mountain ridges while acquiring knowledge of medicinal herbs and distributing talismans throughout the country to bestow medicines.
They trained their bodies in the rich nature of the mountains and fields, and became well informed as they traveled around the country.
The ninja's extraordinary leaping, running, hiding, medicine-making, and mental unification techniques were all based on the daily lives of the people living in the area, as well as their knowledge and skills in their daily occupation, and ninjutsu was not a ridiculous art.
The book "Bansenshukai", a book of ninjutsu secrets written by Yasutake Fujibayashi in 1676 (Enpo 4), also describes the use of gunpowder, medicines, and other chemicals, and the goma practices by the Yamabushi of Aburitsu Shrine, a place of unity among the Koga people fostered by the Yamabushi. Koga is a rocky place for the practice of medicine, witchcraft, astronomy, and various ninjutsu, but it was the advanced technology and religious culture nurtured in Iga and Koga, as well as the diverse lifestyles of its people, that gave birth to ninjutsu there.