One of the Takeda Four Generals. Known as the creator of the "Red Guard," unifying his troops in all-red armor. Small in stature yet feared with the saying "when Yamagata moves, enemies flee." He remained the Takeda core after Shingen's death, dying heroically at the Battle of Nagashino (1575). The Red Guard tradition was later inherited by Ii Naomasa, becoming the symbol of Tokugawa's Four Generals as the "Red Guard of Ii."

Despite his small frame, he was the most daring on the battlefield. As one of Shingen's most trusted generals, he always stood at the frontline.

He left his mark on Sengoku history as the creator of the Red Guard. After the Takeda fell, the tradition was inherited by Ii Naomasa serving Tokugawa Ieyasu, celebrated throughout the Edo period as the mightiest military uniform.