 Tsunehisa leveraged Mōri Motonari to have him attack Kagamiyama Castle, the economic center of the Ōuchi in Aki, which caught the Ōuchi off guard.Motonari had earlier served as custodian for Mōri Kōmatsumaru, head of the Mōri clan.Yoshioki responded by dispatching troops to Aki and Iwami provinces.