Discontented with his succession and in favor of Mototsuna AIO who was Motonari's half brother, a group of senior vassals, including the clans of Saka and Watanabe, rose in revolt, supported by Hidetsuna KAMEI who was chief retainer of the Amago clan and who was guided by Tsunehisa AMAGO.
この時、元就の継承に不満を持った坂氏・渡辺氏等の有力家臣団の一部が、尼子経久の指示を受けた尼子氏重臣・亀井秀綱支援の下、元就の異母弟・相合元綱を擁して謀反を起こした。