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.
As with most of Basilisk's characters, despite retaining his major character traits Yashamaru's character is more expanded upon in the anime than he is in the manga. As the flashbacks featuring him only occur in the anime, his role in the original manga is much smaller with significantly less insight into his personality.
Yashamaru was in the live-action movie Shinobi: Heart Under Blade. There are some differences in that he is not romanticly involved with Hotarubi, only speaks a few words during the entire movie, is very aloof, keeps his long hair, and is somewhat androgynous. He also wears an outfit with extremely long sleeves, but his use of garrote wires remain the same.
In the novel, after realizing Danjou had grabbed his scroll, Yashamaru runs all the way back to Sunpu only to find Ogen and Danjou's dead bodies floating in the river. His affections for Hotarubi and abilities remain the same. However, instead of using multiple wires, Yashamaru wields a single thin piece of rope that he keeps hung from his belt when not in use. He's also described as having shining black eyes and cheeks the color of cherry blossoms.