Ninja can also be interpreted as the name given to someone who mastered and explore the martial art ninjutsu. Defense and nin jutsu means the art or way. The word ninja is taken from the word Ninpō. Po means the philosophy of life or in other words Ninpō is the highest philosophy of ninjutsu martial science on which the life of a ninja. So the ninja will always be alert and Integrate the principles of Ninpō.
