When the Genko War, a war whose object was to overthrow the Kamakura bakufu (Japanese feudal government headed by a shogun), broke out in 1333, Yorinao joined his father Sadatsune--both of whom were in support of the war--in a campaign to destroy Hidetoki HOJO, the chinzei tandai (military governor) of Hakata and the force of the Hojo clan in Kyushu.
1333年（元弘3年）に鎌倉幕府討幕運動である元弘の乱が起こると賛同し、父の貞経に従って九州における北条氏勢力であった博多の鎮西探題北条英時を滅ぼす。