It was from the middle of the 15th century when Sadamori MIZUNO set his base in Ogawa, Chita County, Owari Province (Ogawa, Higashiura-cho, Chita County) that the Mizuno clan began expanding their power.
戦国期において水野氏が勢力を伸ばすのは、15世紀中頃、水野貞守が尾張知多郡小河（知多郡東浦町緒川）に拠点を置いたのに始まる。