Also, he made peace with the Hojo clan, but the conclusion of the Kosun Alliance triggered the failure of the Sunso Alliance (an alliance between the Imagawa clan in Suruga Province and the Hojo clan in Sagami Province), and the Imagawa clan and the Hojo clan were involved in a dispute (the Kato War).
さらに北条氏とも和睦するが、甲駿同盟は駿相同盟の破綻を招き、今川と北条は抗争状態となる（河東の乱）。