Because of the particularity of the profession, ninjas are usually associated with the dark, and their whereabouts are secretive, so it is difficult for outsiders to pry into their internal organization. Therefore, the records about the history of ninjas are very limited, and their origins can not be verified for a long time. According to legend, the first one who sent ninjas to complete the mission was shengdetaizi in the flying bird era. In the later times, ninjas activities were constantly found in various regions, but their names were different, It was not until the Edo era that the term "Ninja" was established, and it is still used today.
Many people have the impression that Ninja is a black tights, as sexy as a cat. This is actually influenced by the concretization of movies and TV series. In many cases, pure black costume will make the outline clearer. Therefore, ninja's general costume is actually dark blue or soy sauce purple, and it will be changed into gray or tan when it comes to bright and starry nights.