Ninja

Ninja (ニンジャ) are demigod-like beings who once ruled Japan in its Heian period. They erased themselves from history after performing the mysterious hara-kiri rites in the Golden Kinkaku Temple, storing their souls. However, in modern-day Neo-Saitama, ninja have been resurrected. All modern ninja are possessed by a Ninja Soul.

All ninja must perform an aisatsu (greeting) to start a fight save for a single sneak attack. If both ninja are aware of each other and do not perform an aisatsu before a fight it is shitsurei (impolite), and if a ninja attacks during an aisatsu it is sugoi shitsurei (super impolite).

Basic Laws of Ninja Souls

1. The majority of ninja souls lose their memories and ego during the possession, only retaining the karate and jitsu. An exception is made for especially powerful souls.
2. A ninja soul may only possess a person of the same gender.
3. A ninja soul may only possess a living being (if the soul is forced into a dead body, a zombie-ninja is born).
4. The person who becomes a ninja cannot have children, be it with a mortal or another ninja.
5. A ninja cannot become human again. If the ninja soul is extracted, the ninja dies.
6. During the possession, the ninja soul regenerates any wounds at tremendous rate, even able to heal mortal wounds.
7. The person who becomes a ninja does not age, though it is also very likely that the aging process is greatly slowed down.