Motoharu always joined the battles in which the Kagawa clan was involved, such as the Battle of Zentsuji, the Battle of Kanakura and Sanshu Heitei-sen (the battle to suppress Sanuki Province) of the Chosokabe clan, and played a lively part as a diplomat when Yukikage KAGAWA secretly communicated with Nobunaga ODA.
善通寺合戦や金倉合戦、長宗我部家の讃州平定戦など香川氏の関わる戦には常に参戦し、また、香川之景が織田信長に通じる際には外交官としても活躍している。