Head of the Hiraga clan, provincial lords who ruled Takaya-ho in Aki Province (present-day Takaya, Higashihiroshima City). Around 1403, when Yamana Mitsuuji became the newly appointed military governor (shugo) of Aki, Hiraga Hiroaki resisted him and held out at his stronghold, Misonoujou Castle. Despite losing his sons Tomomasu, Koremasu, and Koremoto over a three-year siege, he repelled the Yamana forces with the support of allied local warrior bands. Misonoujou remained the Hiraga clan's base for roughly two more centuries.

An unyielding provincial lord who refused to submit to the pressure of a shugo daimyo, holding out under siege even as he lost his sons one after another. He also possessed the diplomatic skill to build alliances among neighboring local warrior bands.

The three-year siege at Misonoujou Castle stands as a symbolic episode of Aki's provincial lords resisting shugo authority during the Muromachi period, preserved in local history.