Taking advantage of the death of Yoshisuke WAKIYA, who supported the Yoshino Imperial Court (Southern Court), Yoriharu attacked Iyo Province (currently Ehime Prefecture) to drive the Odachi clan out of power and stood in opposition to the Kono clan, which held political power in Iyo.
さらに吉野朝廷の脇屋義助の死に乗じて伊予国(愛媛県)へ進攻して大館氏らを駆逐し、伊予の豪族であった河野氏と対立する。