In early 1865, Hirata was a high-ranking official at the Tsushima domain mansion in Kyoto. Previously a supporter of Ôura Norinosuke's sonnô jôi faction, he decided that such a position was no longer tenable given the weakness of Chôshû domain, the shift towards a more conservative faction within shogunate leadership in 1863-1864, and the strength of the Westerners, and so fell in line with supporting his close friend Katsui Gohachirô, who seized power in Tsushima in late 1864.
Hirata soon turned against Katsui, however, when he learned of the violent methods of Katsui's coup, which ended in the deaths of nearly one hundred people associated with Ôura's family or faction. Extolling the virtues of the return to imperial rule, he recruited the support of agents from Chôshû, Satsuma, Fukuoka, Hirado, and Ômura domains, as well as the support of court noble Sanjô Sanetomi, to topple Katsui's pro-shogunate faction.
Sanjô sent an envoy to Tsushima along with several men from Chôshû, who asked Katsui to step down; he agreed to do so, and daimyô Sô Yoshiakira, who had been pressured to accept Katsui's coup to begin with, supported his resignation. Katsui and several of his supporters fled, but were captured and killed, and Hirata took power. His support from Satsuma, Fukuoka, and Chôshû soon dissolved, however, and some of Katsui's remaining supporters turn around and killed Hirata in 1865/11, only weeks or months after his successful coup, leaving one of Hirata's allies, Higuchi Kennosuke, to assume control. Higuchi was then killed, in turn, in 1867/3.
- Robert Hellyer, Defining Engagement, Harvard University Press (2009), 229-230.