After a while, a successive dispute occurred within the Mariya clan between Nobutaka MARIYA & his younger half brother Nobumasa MARIYA. When Yoshiaki intervened in the dispute, he brought Yoshitaka SATOMI to his side, backed up Nobumasa, and expelled Nobutaka.
やがて、真里谷氏内部で真里谷信隆と真里谷信応兄弟による家督争いが起こると、義明は里見義堯を自派に引き入れて信応を支持して信隆を追放するなど、巧みに真里谷氏の争いに介入する。