In 1507, together with the Amago clan, the Mitoya clan joined the army for Kyoto headed by Yoshinori OUCHI who served the previous shogun, Yoshitane ASHIKAGA, but Tsunehisa AMAGO returned home earlier than others from the battle in Kyoto which had been drawn into a war, began invading Ouchi's territory where Yoshinori was absent for the war, starting their confrontation with the Ouchi clan.
永正4年（1507年）に前将軍足利義稙を奉じた大内義興の上洛軍に、尼子氏ともども三刀屋氏も従ったが、泥沼の戦いを続ける京の戦乱よりいち早く帰国した尼子経久は義興不在の大内領への侵略を開始、大内氏との全面的な対立が始まった。