- It is theorized that the ninja could have its roots going as far back as the late Heian period, which ended in the late 12th century.
- The mainly accepted history of the ninja is that it began during the Sengoku period, during the 15th century, from the Mie (then called Iga) prefecture and the city of Kōka (or Kōga) in the Shiga prefecture.
- The most notable of our manuals is the Bansenshukai ("Sea of Myriad Rivers Merging"), written around 1676. It focuses on military strategy and weaponry, as well as philosophy and astronomy, based off of the Chinese.
I hope that this is a sufficient bit of into for you!