Collapse on the Second Floor
The Collapse on the Second Floor (Nikai kuzure no hen) was an incident associated with internal conflict in the Ōtomo clan involving an attack on the second floor of the Ōtomo residence in Bungo Province. The incident occurred on 2/10 of Tenbun 19 (1550).
Ōtomo Yoshiaki, a sengoku daimyō and the twentieth head of the Ōtomo clan, intended for his eldest son, Ōtomo Yoshishige (later known as Ōtomo Sōrin), to become his successor. However, his third son (born to a consort) named Ōtomo Shioichimaru aspired to inherit the clan, so he attempted to remove Yoshishige from the line of succession. Consequently, a power-struggle broke out between members of the clan split into two factions – those supporting Yoshishige and those favoring Shioichimaru.
Yoshiaki called upon several of his senior retainers, including Kozai Yamato-no-kami, Saitō Nagazane, Tsukumi Mimasaka, and Taguchi Akichika to confer in regard to the attempt to remove Yoshishige. All of them supported Yoshishige and persuaded Yoshiaki to maintain his position. Nevertheless, Yoshiaki and Shioichimaru’s mother conspired with a trusted retainer named Nyūta Chikazane to enable Shioichimaru to become Yoshiaki’s successor. Primary supporters of Yoshishige, including Yamamoto-no-kami and Nagazane, were murdered.
Owing to these events, Mimasaka, Akichika, and others in the faction advocating for Yoshishige felt their lives endangered so, on 2/10 of 1550, these retainers 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. Mimasaka and Akichika 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. 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.
Nyūta Chikazane, who had supported Shioichimaru, fled with the assistance of Aso Koretoyo from Higo Province, but was later slayed by the Aso clan. 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 regarding the governance of his territory. Other than the Taguchi clan, the members of other clan retainers were executed in a tragic end.