Are ninjas a myth or did they really exist?

Yes, but not in the form popularized in contemporary media. Historian Stephen Turnbull wrote a book on the subject, he's a student of feudal-era Japan primarily. The idea of the “ninja” we have today came about during the period AFTER the Meiji Restoration that eliminated the caste system of Japan and the Samurai. read more

They really did exist. They came to be identified as ninja sometime in the fifteenth century. Generally they were more rare than literature imagines. The daimyo Oda Nobunaga (died June 21, 1582) destroyed most of the ninja villages in Iga and Koga province and killed off many ninja. read more

Yes they really existed. They were mercenaries following a different code than the Samurais. They were usually used by the governement for missions of reconnaissance, spying, or assassinations. You could sort of say that they were the equivalent of the current C.I.A or Secret Services in United states. Just that it was in Japan 400 years ago instead. read more