Miyabe Keijun served as a bushō and daimyō during the Sengoku and Azuchi-Momoyama periods.

Origins and service as a retainer of the Azai and the Toyotomi

Keijun originated from a local family of means in the village of Miyabe in the Azai District of Ōmi Province.  Originally, he became a warrior monk affiliated with the Enryaku Temple on Mount Hiei near Kyōto.​  Keijun was born as the son of Doi Sanehide, a kokujin, or provincial landowner, in Samegai in the Sakata District of Ōmi.  His family were descendants of the Doi clan from the Kanmu-Heishi.  Keijun was adopted by Miyabe Zenshōjō Seijun, a priest at the Yusuki Shrine in the village of Miyabe in the Azai District.  He became a monk, practicing his religion on Mount Hiei.

Keijun, however, returned to his hometown of Miyabe to become a retainer of Azai Nagamasa, the sengoku daimyō based in northern Ōmi Province.  Excelling in the military arts, he served on behalf of Nagamasa in battles against Oda Nobunaga.  Keijun came into conflict with Hashiba Hideyoshi, the commander in charge of Yokoyama Castle, but, in the tenth month of 1572, was lured by Hideyoshi to serve as a yoriki, or security officer.  As evidence of his betrayal, Keijun incurred injuries after being shot with arquebus fire during an assault on Kunitomo Castle which was aligned with the Azai clan.

According to the authenticated biography of Oda Nobunaga known as the Shinchō-kōki, he was ordered by Nobunaga shortly before this event (during the eighth to ninth months) to protect the stronghold in the village of Miyabe.  His base at Miyabe Castle was indispensable for an assault against Odani Castle.  In the eighth month of 1573, Keijun made numerous contributions on the battlefield including the capture of Odani Castle.  During this period, Keijun adopted Hideyoshi’s nephew, Toyotomi Hidetsugu, but, in fact, he appeared to have been a hostage, and, after the fall of the Azai clan, was returned to Hideyoshi.

Contributions during the Invasion of Chūgoku

Thereafter, Keijun was assigned as a security officer for Hideyoshi and, from 1577, participated in the Invasion of Chūgoku.  Keijun primarily served under Hideyoshi’s younger brother, Hashiba Nagahide (later known as Hidenaga), contributing in attacks in the direction of Tajima Province.  When Hidenaga headed toward the Sanyō region, Keijun served in lieu of Hidenaga as the commander-in-charge of forces in the Sanin region.  Around 1580, after the subjugation of the Yamana clan, Keijun was appointed as the lord of Tajima-Toyooka Castle with a fief of 20,000 koku.  During an assault against Tottori Castle, Keijun served on the front lines of the battle against reinforcements of the Mōri army commanded by Kikkawa Motoharu (the second son of Mōri Motonari).

Among those participating in battle against the Mōri under the command of Keijun in the Sanin Region included Araki Shigekata (later known as Kinoshita Shigekata, a former servant of Araki Murashige who switched to the service of Hideyoshi following a revolt by Murashige), Kakiya Mitsunari who supported the Hashiba clan during the pacification of Tajima, and Kamei Korenori, a bushō and daimyō from Izumo Province who operated closely with Yamanaka Yukimori, the leader of the Amago revival army.

Service in Kyūshū and Odawara and succession

In 1582, Keijun was recognized for his military contributions in the Sanin Region, becoming the chamberlain of Tottori Castle in Inaba Province.  The death of Oda Nobunaga in the Honnō Temple Incident posed the moment of highest risk of an attack by the Mōri army against Tottori Castle, but the fact that he was assigned to protect this important base during the Battle of Yamazaki, the Battle of Shizugatake, and while Hideyoshi’s forces were away from the Chūgoku region highlighted the Hideyoshi’s trust in Keijun and the valued placed upon the protection of this location.

In the wake of the Honnō Temple Incident, after Hideyoshi acquired significant power, Keijun was formally appointed as the lord of Tottori Castle with a fief of 50,000 koku.  In 1585, he joined in attacks against Sassa Narimasa,  During the Subjugation of Kyūshū, Keijun accompanied armies led by Nanjō Mototsugu, Kamei Korenori, Araki Shigekata, and Kakiya Mitsunari, and at Taka Castle in Hyūga Province, he repelled the army of Shimazu Iehisa at the Battle of Nejirozaka.  His efforts during this battle won praise from Hideyoshi.  After the Subjugation of Kyūshū, his fief was increased in Inaba and Tajima provinces to 50,971 koku.  Including kokujin from Inaba and Tajima, a total of 5,350 soldiers were under his command.

In 1590, Keijun participated in the Conquest of Odawara.  That same year, he transferred the headship of his clan to his eldest son, Miyabe Nagafusa, but this was in form only, and Keijun did not retire.  Although he participated in fewer battles, he continued to remain engaged in affairs of governance.

Latter years

In 1592, during the Bunroku Campaign, Keijun was stationed in Hizen-Nagoya.  Keijun sought to cross to the Korean Peninsula but was not allowed.  In 1593, after Ōtomo Yoshimune was removed from his position,  Keijun joined Yamaguchi Munenaga to conduct a land survey in Bungo Province.  That same year, he opened the Inaba-Ginzan silver mine in the village of Arai in the Gamō township in the Iwai District of Inaba Province and was appointed by Hideyoshi to manage the mining operations.  In 1594, Keijun participated in the construction of Fushimi Castle.  At this time, his fief was increased by 81,000 koku.  In 1596, he retired owing to old age.  Trusted by Hideyoshi, Keijun served as a member of Hideyoshi’s personal retinue known as the otogishū.  While serving as an advisor to Hideyoshi, Keijun was involved in governing as one of the senior retainers.

Keijun died on 3/25 of Keichō 4 (1599).  There are various theories regarding his age, including sixty-four, seventy-two, or other.