Hirai Sadatake served as a bushō during the Sengoku period. He was a retainer of the Rokkaku clan, a daimyō family based in southern Ōmi Province.
Sadatake was born as the son of Hirai Takayoshi, a retainer of the Rokkaku clan. The Hirai clan was a branch of the Utagenji-Sasaki clan based in the village of Hirai in the Takashima District of Ōmi (or which may have been another village of Hirai in the Kurita District) founded by Hirai Morotsuna, the great-great grandchild of Sasaki Nobutsuna, a bushō from the late Heian period.
Sadatake supported the governance of the Rokkaku clan and, together with Gotō Katatoyo, Gamō Katahide, Mikumo Shigemochi, Shindō Sadaharu, and Megata Tsunakiyo, was a member of a group known as the Six Elders.
Based on records from the Hongan Temple, Sadatake carried significant responsibility. In 1525, he deployed for battle against Azai Sukemasa. In a letter from the eleventh month of 1553, he participated in a settlement with the Azai clan. He was also dispatched as a messenger to the Ishiyama-Hongan Temple. Sadatake served an honorary role to place the ceremonial headwear known as an eboshi on Azai Katamasa (later known as Nagamasa) at his coming-of-age ceremony. Katamasa was the son of Azai Hisamasa, a subordinate to the Rokkaku clan. Later, Sadatake sent his daughter to wed Nagamasa. Together with Nagamasa, Suketada’s daughter bore Azai Manpukumaru, making Sadatake his grandfather.
After growing weary of the autocratic governance of the Rokkaku, the Azai band of retainers removed Hisamasa and backed Nagamasa whereupon Sadatake’s daughter separated and was sent back to the Hirai family.
In 1568, after Oda Nobunaga invaded Ōmi, Suketada abandoned the Rokkaku and surrendered to Nobunaga. His whereabouts are unknown thereafter.