However, after the death of Tadamasa, Nobumoto MIZUNO, an eldest legitimate son, formed an alliance with Nobuhide ODA, who was gaining power in the Owari Province and rebelled against the Matsudaira clan that was under the control of the Imagawa clan.
しかし忠政の死後、嫡男水野信元は、尾張において台頭した織田信秀と同盟を結んで今川氏支配下の松平氏と反目。