Lifespan: 15xx to 7/2 of Tenshō 6 (1578)
Title: Governor of Echizen
Clan: Jinzai – a branch of the Ono clan who were members of the Musashi shichitō (a band of bushi based in Musashi Province whose influence extended to Kōzuke, Shimotsuke, and Sagami provinces)
Lord: Amago Tsunehisa → Amago Haruhisa → Amago Yoshihisa → Mōri Motonari → Mōri Katsuhisa
Father: Jinzai Hisamichi
Wife: [Formal] Daughter of Moriwaki Hisasada
Children: Kagemichi (?)
Jinzai Motomichi served as a bushō during the Sengoku and Azuchi-Momoyama periods. Motomichi was a retainer of the Amago clan based in Izumo Province, and served as the lord of Jinzai Castle, one of ten castles known as the Amago jikki, or Ten Flags of the Amago, which were outlying castles in Izumo intended to serve as a line of defense for the main base of the Amago clan at Gassantoda Castle.
The Jinzai clan originated from the Ono clan of the Musashi shichitō, or Seven Parties of Musashi. In the Kamakura period, Ono Takamichi moved to Jinzai in the Kando District of Izumo upon his appointment as a jitō, or land steward, serving the Kamakura bakufu. In the Jinzai-no-shō, or manor, he managed the villages of Hagasa, Hisa, and Shimizu. Thereafter, his fief was increased by 4,660 koku in Mimasaka Province.
Motomichi served as a commander-in-chief of foot soldiers for the Amago clan – the sengoku daimyō of Izumo. In 1563, he surrendered after an invasion of Izumo by the Mōri army. In 1566, Gassantoda Castle fell and the Amago were eliminated as a sengoku daimyō in Izumo. Motomichi was appointed to serve as the lord of Sueishi Castle in Hōki Province in lieu of his former territory.
In 1569, former retainers of the Amago including Megata Yukinobu decided to rebel, leading to the formation of an army to resuscitate the Amago. This force was led by Amago Katsuhisa, the fifth son and orphan of Amago Sanehisa. Sanehisa was assassinated in 1554 during a purge led by Amago Haruhisa, a sengoku daimyō and the head of the Amago clan. The target of the purge was the shingūtō – a powerful band of Amago bushō who, from Haruhisa’s perspective, posed a threat to his position. The shingūtō were backed by Yamanaka Yukimori, another former retainer of the Amago. Encouraged by Yukimori, Motomichi killed Nakahara Zenzaemon who was serving as an inspector for the Mōri family, and then joined the Amago revival army. In 1570, the Mōri army led by Mōri Terumoto defeated the Amago revival army under the command of Yukimori at the Battle of Fubeyama whereupon Motomichi fled with Yukimori to Kyōto.
In 1577, the Amago revival army came under the command of Hashiba Hideyoshi, a senior commander of Oda Nobunaga, in battle against the Mōri. Motomichi entered Kōzuki Castle in Harima. The Mōri then surrounded the castle with a force of 60,000 soldiers. Hideyoshi did not have as many troops so, without sending reinforcements and upon orders of Nobunaga, he proceeded to attack Bessho Nagaharu at Miki Castle. Having lost the prospect of receiving additional forces, the Amago revival army agreed to have the members of the Amago family kill themselves in exchange for sparing the lives of the soldiers defending the castle, and then surrendered the castle to the Mōri.
In 1578, Motomichi took his own life along with Amago Katsuhisa, Amago Toyowakamaru (Katsuhisa’s eldest son), and Amago Ujihisa (Katsuhisa’s older brother). Memorial towers for Motomichi and his lord, Katsuhisa, at Kōzuki Castle.
Motomichi’s son, Jinzai Matasaburō, served Kobayakawa Takakage. After receiving one of the characters in his name from Takakage, he adopted the name of Jinzai Kagemichi. Following the demise of Takakage, Kagemichi served the Mōri family and participated in the Bunroku-Keichō Campaign, eventually dying in 1610.