Ninjutsu / Jujutsu are traditional Martial Arts that developed through Japan's turbulent history. The necessity to survive required the highest level techniques, mastered and nurtured by the warrior both male and female, to ensure survival both in war and times of peace.
A Ninja is a master of stealth and disguise (Shinobi in Japanese). Just as sunshine filters through a crack in the wall so must the Ninja gathering intelligence.
This same principle is expressed in a Ninpo poem: "If there is a village on which the moon shines, for a person who wishes to see it, it is there."
"The martial artist who practices good etiquette as well as humanism from the moment that he wakes till the moment he goes to sleep exemplifies a code of conduct "Bufu".
The acts of a true Ninja are governed by such precepts."