Kira Yoshiaki served as a bushō during the Sengoku period. Yoshiaki was the head of the Saijō-Kira clan of Mikawa Province. He was born as the third son of Kira Yoshitaka, the prior head of the Saijō-Kira.
Background of the Kira clan
The Kira were a bushi family in Japan. The family was represented by the Mikawa-Kira clan (founded by Kira Osauji, the eldest illegitimate son of Ashikaga Yoshiuji of the Seiwa-Genji clan) and the Oushū-Kira clan (founded by Kira Yoshitsugu, the younger brother of Osauji) later known as the Musashi-Kira clan. Among the many clans across Japan who were members of the Ashikaga family, the Mikawa-Kira clan maintained an elevated status. In the Muromachi bakufu, the Mikawa-Kira were at the head of the Three Families of the Ashikaga (including the Shibukawa and the Ishibashi) of high rank after the Ashikaga shōgun family. A common refrain was that if the Ashikaga shōgun family ended, then next in line would be the Kira, and after the Kira, the Imagawa. The Kira were of higher status than the Three Deputy Families (the Shiba, the Hosokawa, and the Hatakeyama) who were also members of the Ashikaga shōgun family. As a result of their status, however, the Kira were restrained from participating in the affairs of the bakufu or from establishing hereditary domains as a shugo daimyō.
In the Hazu District of Mikawa, the Mikawa-Kira manor covered areas on the east and west sides of the Yahagi River. During the Nanboku period (1336 to 1392), the clan split between the east and west areas, called the Tōjō-Kira clan (based at Tōjō Castle in Yokosuka) and the Saijō-Kira clan (based at Nishio Castle in Nishio) respectively. In the Sengoku period, both branches of the family in Mikawa and in Musashi maintained limited influence in their respective territories, connecting the families in the Edo period. The Mikawa-Kira clan had elevated status in the Edo period, but owing to the involvement of Kira Yoshihisa in a killing known as the Akō Incident, he was removed from his position and the family name was later revived by a cadet family led by the descendants of his younger brother. Moreover, Yoshihisa’s children included Uesugi Tsunanori who, as an adopted son, inherited the Yonezawa domain of the Uesugi clan and the bloodline continues to the present.
Succession to the Saijō-Kira clan by Yoshiaki
Initially, Yoshiaki’s older brother, Kira Yoshisato, inherited the headship of the Saijō-Kira clan. Upon Yoshisato’s death, he was succeeded by Yoshiaki’s second oldest brother, Kira Yoshiyasu. However, Kira Mochihiro of the Tōjō-Kira clan also died, so Yoshiyasu inherited the headship of the Tōjō-Kira clan while Yoshiaki succeeded Yoshisato as the head of the Saijō-Kira. At this time, Yoshiyasu also attempted to procure the headship of the Saijō-Kira clan, which may have been a cause for a series of conflicts involving the Kira clan.
In 1549, when Imagawa Yoshimoto, a sengoku daimyō from Suruga Province, attacked Oda Nobuhiro, the lord of Anjō Castle and a retainer of the Oda clan, Yoshiaki’s older brother, Kira Yoshiyasu, cooperated with the Oda clan, so he was apprehended by the Imagawa army and taken as a hostage to their base in Sunpu. Yoshiaki, however, cooperated with the Imagawa army, so he was ordered to take over the Tōjō-Kira clan as well. As a result, he unified the Saijō-Kira and the Tōjō-Kira branches and submitted to the governance of the Imagawa family.
Nevertheless, there is another theory with respect to the succession by Yoshiaki of the Kira clan. Under this view, his older brother, Yoshiyasu, was pardoned and returned as head of the family, but, in 1555, rebelled a second time against the Imagawa in an event known as the Furious Drama of Mikawa. In 1557, Yoshiyasu was driven out of Mikawa and, as a result, Yoshiaki became the head of both branches of the Kira family.
On 5/19 of Eiroku 3 (1560), Imagawa Yoshimoto was killed in an attack by Oda Nobunaga at the Battle of Okehazama. This led to a decline in the authority of the Imagawa in Mikawa Province, and Yoshiaki lost his primary backer. Moreover, Matsudaira Motoyasu (later known as Tokugawa Ieyasu) took advantage of the change in circumstances to become independent, launching repeated attacks against the Kira. After numerous clashes, in 1561, the Kira finally surrendered to the Matsudaira clan and, thereafter, were moved to Okazaki.
In 1563, the Mikawa Ikkō-ikki (uprising by adherents of the Ikkō sect) erupted in western Mikawa and persisted for one-half year until 1564. Viewing this as an opportunity to counterattack, Yoshiaki joined forces with the Ikkō sect and faced another showdown against Ieyasu. There is also a theory that he fought back without combining forces with the Ikkō sect. This plan, however, did not succeed, and Tōjō Castle fell. Yoshiaki stayed in Mikawa for a while under difficult circumstances and was then forced to leave the province. He fled to Ōmi Province and, in the end, died in Akutagawa in Settsu Province.
Yoshiaki’s older brother, Yoshiyasu, inherited the headship of the Kira clan while the Matsudaira permitted the Mikawa-Kira clan to survive.