The successor to the Yagyuu family name, the daughter of Koshinori Yagyuu and the granddaughter of Binbokusai Yagyuu.

They were brought up as a male, following the code of the Yagyuu clan, but in later years decided to follow neither femininity or masculinity, but live as only "Yagyuu Kyuubei." During their introduction, they tried to take Tae Shimura as their fiancee, though Shinpachi and the rest stopped them from doing it. Yagyuu still has feelings for Tae, though they remained in friendly ties.

A genius swordsman; surpassing average swordsmen in skills, and is able to hold themself against veteran swordsmen, like Toushirou Hijikata and Gintoki.