>>11791658You need read the books of Ashida Kim, one of the only known actual master ninjas. They were popular at the height of the so-called 'ninja craze'. They reveal many (but not all!) of the mysteries of the ninja.
You might come across articles or other posts disparaging Ashida Kim and those like him but don't be fooled. In the mid-90's the international situation, as well as the public consciousness about the ninja, meant that things were getting a little too hot. So Kim, along with the Black Dragon Fighting Society and other allied secretive martial arts societies orchestrated the rise of the UFC which resulted in a massive shift in the public eye of what actual fighting and martial arts even is. In this way the ninja were able to fade again into the shadows and operate unhindered, shrouded by the disbelief of the public and the surface-level martial arts community itself.