Lord of Wachigaya Castle in Atsumi District, Mikawa Province, and head of the Mikawa Saigo clan. He governed eastern Mikawa from Wachigaya Castle, founded in 1523 as the clan's base. In 1561 he handed the castle to his heir Motomasa and built a new stronghold, Gohonmatsu Castle, to which he relocated. After the clan sided with Matsudaira (Tokugawa) Ieyasu following the Battle of Okehazama, it is said to have faced retaliation from Imagawa Ujizane.

A local lord of eastern Mikawa who maintained his own sphere of influence even under Imagawa dominance. He showed the judgment to align quickly with the Matsudaira side after Okehazama, though he paid for it with Imagawa retaliation.

A descendant of his clan, Lady Saigo (Oai no Kata), later became a consort of Tokugawa Ieyasu and gave birth to the second shogun, Tokugawa Hidetada. The ruins of Wachigaya Castle in Suzuyama, Toyohashi, survive today as a mountain-castle site.