Centuries ago, the emperor of Japan asked his general to protect the Jewel of Amaterasu, a gem said to allow the wielder to control their ki. The gem was so well concealed, that its location was lost with the ascendancy of emperors, and the general's family was eventually reduced to simple farmers, who would later become the Arashikage. For generations, the Arashikage worked as shadowy assassins, using deception to earn their keep as ninjas, as well as developing a reputation for being able to perform impossible tasks.
Later, the Arashikage would continue the deception, financing front businesses to hide their true work as covert operatives, bounty hunters, thieves, and contract killers. Their remote compound was hidden in the mountains of Japan. Only those who truly prove their worth, and commitment to the Arashikage katas and discipline, were allowed full membership into the clan. This was denoted by the tattooing of the clan symbol on the forearm, the 63rd hexagram of the I Ching.
"After completion. Water above fire."