Lifespan: Bunki 2 (1502) to 2/12 of Tenbun 19 (1550)
Rank: bushō, sengoku daimyō
Title: Junior Fourth Rank (Upper), Master of the Office of Palace Repairs
Bakufu: Muromachi – Military Governor of Bungo, Higo, and Chikugo Provinces
Lord: Ashikaga Yoshitane → Ashikaga Yoshiharu → Ashikaga Yoshiteru
Father: Ōtomo Yoshinaga
Mother: Daughter of Aso Korenori
Siblings: Yoshiaki, Shigeharu (Kikuchi Yoshitake)
Wife: [Formal] Daughter of Ōuchi Yoshioki, [Second] Daughter of the Bōjō clan
Children: Yoshishige (Sōrin), Haruhide (Ōuchi Yoshinaga), Shioichimaru, daughter (wife of Ichijō Fusamoto), daughter (wife of Kōno Michinobu), Chikasada, daughter (wife of Yoshihiro Akimasa), daughter (wife of Tomiki Akihide) (?), daughter (wife of Kotabe Shigemoto)
Ōtomo Yoshiaki served as a bushō and sengoku daimyō. Yoshiaki was the twentieth head of the Ōtomo clan, the sengoku daimyō of Bungo Province in Kyūshū.
In 1502, Yoshiaki was born as the son of Ōtomo Yoshinaga, the nineteenth head of the Ōtomo clan. Yoshiaki was first named Chikayasu, then Chikaatsu before adopting the name of Yoshiaki as noted below.
In 1515, after the retirement of his father, Yoshinaga, Yoshiaki became the twentieth head of the clan. Owing to his youth, Yoshiaki received support from Yoshinaga until Yoshinaga’s death in 1518. That same year, Kutami Chikamitsu launched a rebellion with the aim of backing Daishōin Sōshin (the sixth son of Ōtomo Chikatsuna), but he was subdued.
Thereafter, Yoshiaki was guided by his grandfather, Ōtomo Chikaharu, until Chikaharu’s death in 1524. On 3/9 of Daiei 4 (1524), Yoshiaki was conferred the title of Master of Master of the Office of Palace Repairs. He then received one of the characters from the name of Ashikaga Yoshiharu (the twelfth shōgun of the Muromachi bakufu) and adopted the name of Yoshiaki.
In the past, the Ōtomo clan was beset by prolonged succession disputes, but, in the era of Yoshinaga, these were brought under control so Yoshiaki could actively pursue the expansion of the clan’s territory. This included the neighboring province of Higo which did not have a large power. The well-known Kikuchi clan was weakened by internal conflicts so Yoshiaki arranged for his younger brother, Kikuhōshimaru to be adopted by Kikuchi Takekane as the designated heir of the Kikuchi, enabling the Ōtomo to govern Higo through him. After undergoing his coming-of-age ceremony, Kikuhōshimaru adopted the name of Ōtomo Shigeharu and was welcomed to Waifu Castle.
In 1520, retainers from the Kikuchi clan under pressure from their lords in the Ōtomo clan to expel Takekane on the pretext of his being an imbecile. Shigeharu then became the head of the Kikuchi family. Serving as the twenty-sixth head of the Kikuchi, Shigeharu changed his name to Kikuchi Yoshimune and then Kikuchi Yoshitake. Shigeharu, however, did not get along well with Yoshiaki, and, in the end, aimed to become an independent daimyō, leading to a blood feud between Yoshiaki and Shigeharu.
On 3/29 of Daiei 6 (1532), Yoshiaki was promoted from Senior Fifth Rank (Lower) to Junior Fourth Rank (Lower). On 7/4 of Kyōroku 5 (1532) he was promoted to Junior Fourth Rank (Upper).
In the fourth month of 1534, Ōuchi Yoshitaka invaded and, for a while, pressed hard against the Ōtomo who had fewer forces in an event known as the Battle of Seibagahara, but it ended in either a draw or strategic victory for the Ōtomo. In 1538, Yoshiaki relied upon Ashikaga Yoshiharu to mediate a reconciliation with the Ōuchi. Yoshiaki established a close relationship with the Ashikaga shōgun family and, in 1543, was appointed as the military governor of Higo on behalf of the Muromachi bakufu.
At the time, Yoshiaki became concerned after Itō Yoshisuke and Arima Haruzumi (who were at a lower level of status) received one of the characters from the name of Ashikaga Yoshiharu, so, in 1539, he protested to the Muromachi bakufu. Yoshiaki asserted that, as daimyō families in the western provinces, the Ōuchi and the Ōtomo be permitted to have the title of daibu, or high steward, corresponding to the highest class, while the Shimazu, the Kikuchi, the Kyūshū-Chiba and the Shōni be permitted to receive a character from the name of the shōgun and official appointments. Other families were to be treated as servants to the daimyō and not permitted to receive the characters from the name of the shōgun or official appointments. As an exception, the Itō clan would be allowed to use the name conferred and be appointed as the Governor of Yamato. In 1545, Yoshiaki, however, could not prevent Sagara Yoshishige and Sagara Haruhiro from receiving characters from the name of Ashikaga Yoshiharu or official appointments as mediated by Ōuchi Yoshitaka. The Ōuchi regarded the Ōtomo as a lower-ranking family than themselves, which is believed to be a factor causing conflict between the families.
In 1550, Yoshiaki attempted to transfer headship of the clan to his cherished third son, Ōtomo Shioichimaru, instead of his eldest son, Ōtomo Yoshishige, who was rough and not widely respected. Yoshiaki then plotted with a trusted retainer named Nyūta Chikazane and proceeded to kill retainers who favored Yoshishige, including Kozai Yamato-no-kami and Saitō Nagazane (Shigezane’s father). The succession of killings triggered fear among the retainers in Yoshishige’s camp who then struck back. On 2/10 of Tenbun 19 (1550), in an event known as the Collapse on the Second Floor, Taguchi Akichika, a member of the kabanshū, or elders of the Ōtomo clan, and leader of the faction supporting Yoshishige, together with Tsukumi Mimasaka-no-kami, attacked Yoshiaki, Shioichimaru, and his mother where they slept on the second floor of the Ōtomo residence. Shioichimaru, his mother, and two of Yoshiaki’s daughters perished in the incident. The attackers met a valorous end at the site of the attack. Meanwhile, Yoshiaki died several days later from injuries sustained in the attack after recording his final wishes concerning the governance of his domain. He was forty-nine years old. Following his demise, retainers led by Bekki Akitsura (later known as Tachibana Dōsetsu) rallied behind Yoshishige to serve as the next head of the Ōtomo clan.
Yoshishige viewed Nyūta Chikazane as a ringleader of the plot and, upon his orders, had Akitsura pursue Chikazane. Chikazane fled Higo Province and sought the protection of his father-in-law, Aso Koretoyo, but Koretoyo loathed him for the acts committed and Chikazane was killed. After the attack on his family members, Yoshishige executed those involved, but instability within the clan persisted. In 1553, Yoshishige discovered a plot by Hattori Ukyō-no-suke and other retainers to assassinate him. Yoshishige’s mother was the daughter of the Bōjō family, a kuge, or family of nobility. Alternatively, she may have been the daughter of Ōuchi Yoshioki, in which case the retainers may have sought to remove Yoshishige as a means to reduce the influence of the Ōuchi.
According to some sources, the incident is characterized as a reckless response by some of the supporters of Yoshishige who felt cornered, but uncertainties remain. One theory is that Yoshishige was operating behind the scenes, and that Yoshishige (rather than Yoshiaki) recorded what purported to be Yoshiaki’s final wishes by which he recognized Yoshishige as his successor. The fact that the document was formally written does not suggest it was written by someone in their dying moments. Other than the Taguchi clan, the members of other clan retainers were executed in a tragic end.
Under traditional views of this incident, Yoshishige was not involved. However, a more recent theory is that he was involved and there is a high likelihood that Yoshiaki was killed on the night of the attack.