大和国
Munetoshi was born Yagyū Shinsuke in 1529 in Yagyū Village (present day Yagyū, Nara) in Yamato Province. His father, Ietoshi, was a minor landed lord. When Munetoshi was 12, Ietoshi joined a general named Kisawa Nagamasa in contesting the growing power of the warlord Miyoshi Chōkei. However, Kisawa was killed in battle, and the Yagyū found themselves on the defensive. With over half of Yamato Province under his control, Miyoshi left the rest of the conquest to his lieutenant, Tsutsui Junshō.