Immediately after this incident, when MINAMOTO no Yoritomo, who had been banished to Izu Province, raised an army, Aritsuna joined the army under Yoritomo, so as to destroy his grandfather's enemy, the Taira clan.
直後に同地で配流の身であった源頼朝が挙兵するとその麾下に入り、父祖の仇敵である平家討滅を目指すこととなる。