Lifespan: Unknown to 12/5 of Eiroku 4 (1562)
Other Names: Yorisada, Maita-dono, Setagaya-dono
Title: Junior Fourth Rank (Lower), Assistant Captain of Imperial Guards of the Left Division
Lord: Hōjō Ujitsuna → Hōjō Ujiyasu
Father: Kira Shigetaka
Wife: [Formal] Daughter of Hōjō Ujitsuna; [Consort] Tokiwa (daughter of Ōhira Dewa-no-kami), others
Children: Three children
Adopted Children: Ujitomo
Kira Yoriyasu served as a bushō during the Sengoku period.
Yoriyasu was born as the son of Kira Shigetaka of the Musashi-Kira clan. Owing to residences that he kept at Setagaya Castle in Musashi and Maita Castle in the Kuraki District of Musashi, he was also called Lord Setagaya or Lord Maita.
In the first month of 1524, when Hōjō Ujitsuna of Sagami captured Edo Castle from Uesugi Tomooki, he obeyed the Gohōjō clan. In 1533, Yoriyasu participated in the construction of the Tsurugaoka-Hachiman Shrine by Ujitsuna, and shipped lumber by sea route from Maita to Sugita and then, with over 50,000 laborers, transported the materials to the Hachiman Shrine. Yoriyasu wed as his formal wife the daughter of Ujitsuna, and, on 6/7 of Tenbun 8 (1539), held prayers for the safe delivery of their child. He is surmised to have been married at this time.
In the eleventh month of 1546, he was conferred the title of Junior Fourth Rank, Assistant Captain of Imperial Guards of the Left Division. In 1548, he received a character from the name of Hōjō Ujiyasu and changed his name to Yoriyasu. Nevertheless, by 1554, he relinquished the title of Assistant Captain of Imperial Guards of the Left Division. The period that Yoriyasu used this title overlapped with a period of tension between the Hōjō clan and the Ashikaga family of the Koga kubō. In 1554, Ashikaga Haruuji, the fourth Koga kubō, was attacked at Koga Castle and incarcerated by Ujiyasu. Ujiyasu may have had Yoriyasu carry this title with connections to the Koga kubō as a display of the authority of the Kira clan in lieu of Haruuji. Ultimately, Ashikaga Yoshiuji became the fifth Koga kubō with the support of Ujiyasu and Yoriyasu ended his use of the title after this period of tension waned.
Yoriyasu did not have a natural son so, in the twelfth month of 1560, he adopted Horigoe Ujitomo, the son of Horigoe Rokurō. In the second month of 1561, he had Rokurō succeed to the headship of the clan.
Yoriyasu died on 12/5 of Eiroku 4 (1562) and was buried at the Shōkoku Temple in Maita in Musashi Province.
Relationship with the Hōjō clan
Yoriyasu served the Hōjō clan, but, owing to their association with the Ashikaga shōgun family he was treated as a house guest rather than as a retainer. He was exempted by the Hōjō from assorted taxes, and the Kira family was permitted to use their own seal on documents. Moreover, conferring the second character from the name of Ujiyasu to Yoriyasu indicated special treatment.
Nevertheless, as the status of the Hōjō clan increased, and as their power grew, the situation gradually changed. From the Kōji era (1555 to 1558), Hōjō Ujiyasu issued orders directly to retainers of the Kira family and, over a period of time, this band of retainers disintegrated. In the era of Kira Ujitomo (who succeeded Yoriyasu), the Kira were folded into the Hōjō as retainers, including for military service. From another perspective, the band of retainers of the Kira began to serve both families, but were not fully incorporated into the band of retainers dedicated to the Hōjō.
Kira Ujitomo, who was adopted by Yoriyasu and succeeded to the headship of the clan, was the natural son of Horigoe Rokurō of the Tōtōmi-Imagawa clan and Sakihime, the daughter of Hōjō Ujitsuna. Owing to the origins of his mother from the Hōjō, there is a view that the Hōjō forcibly intervened and recast the Kira clan as their retainers or that the Hōjō overrode the authority of the Kira and annexed their territory and made the retainers their own. On the other hand, Ujitomo’s father originated from the Horigoe (a branch of the Kira), so it is asserted that efforts were made to preserve the authority and nobility of the Kira based on their affiliation with the Ashikaga shōgun family, including the culture and formalities of a clan possessing a network across a broad area of the Kantō.