Confrontation of Surnames
The Confrontation of Surnames (Seishi tairitsu jiken) was a conflict between branch members of the Ōtomo clan who carried the Ōtomo family name and seal against other members of the clan who had a different family name and seal. Those in the latter group who carried a different name and seal were military families residing in Bungo Province prior to the arrival of the Ōtomo.
In the fifth month of 1556, family members with a name and seal other than Ōtomo rallied together to raise arms against important policies of the branch families who carried the Ōtomo surname. Friction between the two groups existed within the clan from an earlier time, so Ōtomo Yoshiaki, a sengoku daimyō and twentieth head of the clan, had pledged in his last testament that one-half of the council of clan elders, known as the kabanshū, would be chosen from the group who carried a name other than Ōtomo. However, his son, Ōtomo Yoshishige, the twenty-first head of the clan, favored a council of elders with the Ōtomo name, so senior retainers such as Obara Akimoto were removed from the council. In the case of Akimoto, this occurred despite his contributions to pacify Higo Province.
The revolt by members of the family with a name other than Ōtomo also occurred near the primary residence of the Ōtomo clan in Funai. This caused Yoshishige to take refuge in the stronghold of Usuki Castle for a while, but members of the clan who carried the Ōtomo name fought back and killed Honjō Shinsaemon-no-jō Munetsuna, Nakamura Shinhyōe Naganao, and Kaku Kii-no-kami Koreshige, while Saeki Korenori fled to Iyo Province in Shikoku. Intrepid commanders such as Akimoto sheltered in Nankan Castle and exhorted the defenders to fight valiantly, but the attackers set fire to the castle, and after tending to the women and children, Akimoto joined his men to rush out of the castle and perish in battle.