Ninja or Ninja are secret agents or mercenaries of feudal Japan. Ninja's functions include espionage, sabotage, infiltration, assassination and guerrilla warfare. Their secret method of waging unconventional wars is considered disgraceful, and under the samurai, the samurai abide by strict rules about honor and combat. Shinobi itself, a specially trained group of spies and mercenaries, appeared in the Sengoku period of the 15th century, but the earliest age may have existed as early as the 12th century.

During the turbulent period of the Warring States period (the 15th-17th century), mercenaries and spies were active in the area near IGAD province and kega village, and it was from the clans in that area that we learned about ninjas. After the unification of Tokugawa Shogunate (17th century), ninja gradually faded out of people's sight. Many Shinobi manuals, usually based on Chinese military philosophy, were written in the 17th and 18th centuries, most notably bansenshukai (1676).

By the Meiji Restoration period (1868), the tradition of Ninja had become a popular topic of imagination and mystery in Japan. Ninjas play an important role in legends and folklore. They are related to legendary abilities such as invisibility, walking on water and controlling natural elements. As a result, their perception of popular culture is often based more on such legends and legends than on historical accurate spies during the Warring States period.