Ninja, also called Shinobi, were a caste of warriors in ancient Japan.
"Ninja" have been glamorized as an icon of alternative pop culture in recent years. They appear frequently in video games, as well, alongside samurai as an alternative warrior caste. The "ninja" in modern pop culture is secretive, killing by stealth, and employing deception as a means to achieve their goals.
Ninja were in reality mostly mercenary assassins who tended to organize themselves in clans.
The first Day of the Ninja was held on December 5, 2003.