Masayasu was the son of hatamoto Inaba Masakichi, from whom he inherited the 5000 koku territory of Aono han in 1656. He served as a page and clerk for some time, before being summoned by the shogunate to oversee irrigation projects in the provinces of Kawachi and Settsu.
Masayasu was a scion of the Inaba clan, inheriting the Aono han domain in 1656 from his father. He progressed through various roles before being appointed by the shogunate to supervise irrigation works in the provinces of Kawachi and Settsu.