Shizukuishi Hisaaki served as a bushō during the Sengoku period.
The Shizukuishi were an illegitimate branch of the Shiba clan, members of the Ashikaga clan having the same founder as the Ashikaga shōgun family, descended from the Kawachi-Genji lineage who were a branch of the Seiwa-Genji.
Hisaaki had the honorary name of Izumi and was either the son or grandson of Shizukuishi Akisada, the lord of Shizukuishi Castle in Mutsu Province.
In the era of his grandfather, Akisada, the family adopted the Shizukuishi surname and the title of gosho, or prince, while Hisaaki was the third-generation head of the family. The Shizukuishi were loyal the Kōsuiji-Shiba (the main branch of the clan) and resisted an invasion by the Nanbu clan into the territory of the Shiba. Owing to the decimation of the Ashikaga shōgun family descended from the main branch of the Shiba, the family lost its authority and, together with the Shiba clan, was vanquished. In 1588, after the end of his lord’s family, Hisaaki lived in seclusion in Hanamaki. Later, during the Keichō era (1596 to 1615), he was engaged by Kita Nobuchika (a chief retainer and family member of the Nanbu clan) and served as a retainer of the Nanbu.