The son of Yamana Masauji, Tokiuji served Ashikaga Takauji as shugo of Hoki, later gaining Tango, Izumo and Oki in 1341. During the Kanno Disturbance he sided with Ashikaga Tadafuyu, but returned to shogunal allegiance in 1363, resuming the shugo posts of Hoki and Tanba. In the Bunwa era (1352-1355) he built Futagamiyama Castle as shugo of Inaba. His son Ujifuyu inherited the Inaba post, and at its height the Yamana clan held shugo posts in eleven of Japan's sixty-six provinces, earning the nickname "Lord of a Sixth of the Realm." He died in 1371 at 69.

A strategist who skillfully navigated the turmoil of the Northern and Southern Courts period, at times aligning with rival factions, to rapidly expand Yamana power across the Sanin region.

By building Futagamiyama Castle as the shugo headquarters of Inaba, he laid the foundation for Yamana rule over the province. His clan later grew to control eleven of Japan's sixty-six provinces.