We are often told about the lack of credible information about ninja. But in fact the situation is not so desperate. Nowadays we have by hand several dozens of ninja treatises the most famous of which are “Bansenshukai”, “Ninpiden” and “Shoninki”, which all were published in Japan several time each. We have a detailed account of Oda invasion to Iga province in “Iranki” with parallel fragments in “Shinchokoki”. We have dozens of reports of shoguns’s o-niwaban and other documents. We have lot of genealogies of many ninja clans - the Hattori, the Fujibayashi, the Momochi and others. And finally hundreds of passages from many gunki-monogatari - “Taiheiki”, “Hojo godaiki”, “Kanhasshu-roku”, “Matsuo-gunki”, “Intoku Taiheiki”, “Taikoki” and many others.

If you would study Japanese historical texts, classical literary texts, real ninjutsu treatises, and works of leading modern researchers of ninjutsu history - Yamaguchi Masayuki, Okuse Heishichiro, Nawa Yumio and others - we will find a different image of ninja and ninjutsu. Here I want to quote from a 18th century book "Buke myomokusho" or “Titles of samurai’s families”:

“Shinobi-no mono execute different espionage work. Therefore they also are named kanja or choja. So, their service is to secretly penetrate to another provinces and find out the real situation in enemy camp, or by mixing with enemy to find out his weak points. Additionally in enemy camp they set fires, and as assassins kill people. These shinobi are used in many cases. They are also named mono-kiki, shinobi-metsuke. If from the first time their duties are not fixed, there are no tasks which they are not given. As shinobi usually common people, “light-legs” (ashigaru), police guards (doshin), rappa, seppa and others are used. Near Kyoto in Iga province and in Koga [district of province] Omi there were many jizamurai, after Onin years (1467-1477) they organized their own bands (to) and fought during the day and during the night, they also stealed and robbed. Many of them became masters in theirs art of espionage (kancho-no jutsu), after this feudal lords (daimyo) of all clans began to hire such jijamurai. The usual practice was to hire them as spies (shinobi). And they were named Iga-mono - Men from Iga - and Koga-mono - Men from Koga” (translation from old japanese from: Koji ruien. Tokyo, 1969, v. 43, p.346).