Yashamaru was chosen to be one of the ten ninja to represent his clan of Iga Tsubagakure against the chosen ten of the rival Kouga Manjidani clan.
A brash and cocky young man, Yashamaru's favored weapon are dozens of strands of garotte wires called Kokujou (black rope, or black binding) which are woven from the hair of young women and alchemically treated with natural oils havested from wild animals, turning them as hard as steel. Yashamaru controls the Kokujou as though they are an extension of his own body, and can use them to tie an opponent up, slice them to pieces, flay them, or even stiffen the wires so they can pierce like needles. The wires are usually kept wrapped around Yashamaru's forearms, but extra wires are tied around his calves in the event his hands and/or upper body becomes immobilized. He also carries a cleaver in a sheathe on his back although his opponents rarely get close enough that he's required to draw it.
Unlike most of the Iga clan, Yashamaru had begun to consider the Hattori truce beneficial as it allowed him a chance to live a peaceful and quiet life with his lover and comrade Hotarubi, whom he planned to marry before the treaty's cancellation resulted in all out war between the clans.