Ouchi Masahiro was born in Japan. He was the eldest son of Norihiro.
Governor of four provinces in western Honshu including Suo and Nagato (Yamaguchi Prefecture).
In the Onin Civil War (1467), he sided with Sozen Yamana and led his troops across the Inland Sea. Landed at Omonoura Beach near Osaka, routed the counterattacking forces of the Hosokawasand entered the capital of Kyoto in triumph.
In 1469, Noriyori Shoni rose in revolt on Tsushima Island and disturbed the order of l fasahiro's provinces. He returned to his domain (1470), led his forces to Chikuzen (Fukuoka Prefecture) and routed the forces of Noriyori. A waka poet, he ruled his provinces with benevolent.