徳川家綱
was a "daimyō" and a teacher of kenjutsu and military strategy in Japan during the Edo period. His highest-ranking pupil was Tokugawa Ietsuna, fourth Tokugawa "shōgun". Munefuyu, who also went by the name Matajūrō, was the third son of Yagyū Munenori. One of his elder brothers was Yagyū Jūbei Mitsuyoshi. His younger brother was Retsudō Gisen, the real person who is fictionalized as Yagyū Retsudō, leader of the "Ura-Yagyū" (Shadow Yagyū), in "Lone Wolf and Cub".