Lifespan: Eishō 10 (1513) to 5/22 of Tenshō 16 (1588)
Title: Assistant Vice Minister of Education, Governor of Mikawa, Vice Minister of Finance, Governor of Dewa
Clan: Iwami-Yoshimi (descended from Minamoto no Noriyori of the Seiwa-Genji)
Lord: Ōuchi Yoshioki → Ōuchi Yoshitaka → Mōri Motonari → Mōri Terumoto
Father: Yoshimi Yorioki
Mother: Daughter of Naitō Hironori
Siblings: Okinari, Takayori, Taketoshi, Chikanobu, Masayori, Yorimori, Yorikazu, Yorizane, Norihiro, sister (wife of Sufu Sukeoki)
Wife: [Formal] Ōmiya-hime, [Second] daughter of Naitō Takaharu, [Consort] member of the Mitsui clan
Children: Hiroyori, Hiromasa
Yoshimi Masayori served as a bushō during the Sengoku and Azuchi-Momoyama periods. Masayori was the head of the Yoshimi clan, a kokujin, or provincial landowner, based at Sanbonmatsu Castle in Tsuwano iin the Kanoashi District of Iwami Province. He served as a retainer of the Ōuchi and, the Mōri clan.
The Yoshimi clan, kokujin in Iwami Province, were a branch of the Seiwa-Genji who were remote descendants of Minamoto no Yorinori, the younger brother of Minamoto no Yoritomo, the first shōgun of the Kamakura bakufu in the middle of the twelfth century.
In 1513, Masayori was born as the fifth son of Yoshimi Yorioki. Initially, he entered the priesthood at the Kōgen Temple in Tsuwano in Iwami. In 1540, his older brother, Yoshimi Takayori, who had inherited the headship of the clan, died unexpectedly so Masayori returned to secular life and succeeded his brother as the head of the clan, marrying Takayori’s widow, Ōmiyahime (the daughter of Ōuchi Yoshioki and elder sister of Ōuchi Yoshitaka). Masayori was an individual of integrity, earning the deep trust of Yoshitaka.
In the fourth month of 1550, after years of disputes over landholdings, Masuda Fujikane attacked Sanbonmatsu Castle and Shimose Castle, but Masayori repelled him.
In the eighth month of 1551, Sagara Taketō visited as a secret messenger of Ōuchi Yoshitaka to Masayori’s territory. On 9/1, Yoshitaka was forced to kill himself in a coup d’état launched by his senior retainer, Sue Takafusa. This event is known as the Tainei Temple Incident. Although the Sue and Yoshimi were both retainers of the Ōuchi, from the time of the Ōnin-Bunmei War, the two clans were arch-rivals, a situation that had not been desired by Yoshitaka. Moreover, Takafusa was the cousin of Masuda Fujikane with whom Masayori disputed over territory, and Takafusa himself was allied with the Masuda. Consequently, Masayori served in the forefront of a rebellion against Takafusa. He also engaged in secret negotiations with Mōri Motonari of Aki Province, urging him to take action.
In 1554, the Ōuchi army launched an all-out assault against Sanbonmatsu Castle, during which Masayori holed-up inside the citadel. The Siege of Sanbonmatsu Castle ended in a settlement upon the condition that Masayori send his son, Kameōmaru (later known as Yoshimi Hiroyori), as a hostage, to the Ōuchi in Yamaguchi. In 1557, during the Subjugation of Bōchō (meaning Suō and Nagato provinces) by Mōri Motonari, Masayori operated in concert with the Mōri army by invading Yamaguchi in Suō. Masayori expelled the Ōuchi forces led by Nogami Fusatada from Watarigawa Castle in the Abu District of Nagato, advanced to Miyanoguchi in the northern part of Yamaguchi, and then captured Yamaguchi. Later that year, after the demise of the Ōuchi clan, Masayori became a retainer of Mōri Motonari and received landholdings in the Yoshika District of Iwami, the Abu and Kotō districts of Nagato, and the Saba District of Suō Province. Similar to the case of Yoshitaka, Masayori earned the deep trust of Motonari as a person of high integrity. In 1571, after the death of Motonari, Masayori was requested by Kikkawa Motoharu (Motonari’s second son) to serve as a deputy to Mōri Terumoto, Motonari’s grandson who inherited the headship of the clan from Motonari.
In 1582, Masayori deployed for the last time for battle at Bitchū-Takamatsu Castle. He then transferred headship of the Yoshimi clan to his son, Hiroyori, and retired at Shizuki Castle in the Abu District of Nagato. On 5/22 of Tenshō 16 (1588), Masayori died in this location at the age of seventy-six. He was buried below Shizuki Castle, but his grave was later moved to the foothills of Mount Kushi in the village of Ōi in the Abu District of Nagato Province.