Lifespan: Unknown to eleventh month of Entoku 1 (1489)
Rank: shugo (Military Governor of Inaba Province)
Title: Assistant Vice-Minister of Civil Affairs
Father: Yamana Masayasu
Adoptive Father: Yamana Yoshinari (uncle)
Yamana Masazane served as a shugo, or military governor, of Inaba Province.
There is a lack of authenticated accounts concerning his birth or adoption. Masazane was the son of Yamana Masayasu, and based on the genealogy of the Yamana clan, he was adopted by his uncle, Yamana Yoshinari. According to one account, Masazane served from an early age in a temple, assisting the monks with their meals.
On 8/13 of 1488, he was appointed the military governor of Inaba Province through the influence of Uragami Norimune, the deputy military governor of Harima Province. Masazane received support from the Akamatsu and others associated with the eastern army who opposed Yamana Toyotoki, the military governor of Inaba. Soon thereafter, Masazane met with Ashikaga Yoshihisa, the shōgun, and, on 8/24, joined the conquest against the Rokkaku clan of northern Ōmi Province.
In Inaba, Mōri Sadamoto, a kokujin, or local family of influence, launched a rebellion in a bid for independence from Toyotoki. In the Second Conflict of Mōri Jirō, Masazane received support from the Mōri clan. Initially, he stayed in Kyōto. In the second month of 1489, he quickly returned to Inaba after learning that the rebels faced difficult circumstances.
Although the actions he took upon returning to Inaba are unclear, Masazane appears to have fought against forces led by Yamana Toyotoki, the prior military governor. However, the support for Masazane as the new military governor was limited. At the Battle of Tokumaru-gawara in the ninth month of 1489, Masazane was defeated after a rebellion by Kitagawa Sanzaemon, a member of the family of Yabe Sadatoshi, a local family of influence.
In the middle of the eleventh month of 1489, a fierce attack by Toyotoki’s army toppled Ichiba Castle in the Yazu District of Inaba. Inside the castle, members of the Yabe clan stopped Masazane from killing himself. Thereafter, he safely escaped from the castle with thirty subordinates including members of the Yabe, successfully reaching the Yabe residence in the town of Wakasa. The residence was then surrounded by Toyotoki’s forces who had given chase. With the forces blocking escape to Harima, Masazane and Sadatoshi took their own lives.