Throughout the tumultuous Sengoku period, they were the rulers of Kariya Castle in Mikawa Province, which also served as the ancestral home of Tokugawa Ieyasu's mother, Odai no Kata (Denzuin).

Following the Battle of Okehaza, the Mizuno clan pledged their allegiance to Ieyasu and became one of the Fudai Daimyo during the Edo period.

Known for their loyalty and service, the Mizuno clan played a significant role in the shogunate, often appointing senior members to key positions.

This theory states that the son of Michitsune Konoe, who held the position of Minister of the Right, resided in Mizuno-mura, Nishi-Sagano (Kazuno District), Yamashiro Province, and adopted the Mizuno family name.

However, due to the early birth of Tomoshige, the son of Ogawa Shigekiyo, he was adopted by Kiyofusa and the family name was changed accordingly.

This marked the beginning of the clan's expansion, as they also established Kariya Castle in Aoumi District, Mikawa Province.

With their power base secured, the Mizuno clan expanded their territory by moving southward to the Chita Peninsula.

As a result of this prevailing trend, Tokugawa Ieyasu's mother, Dentsuin, who happened to be the daughter of Mizuno Tadamasa, was transferred to the Matsudaira clan.

This occurred around 1551 when Nobumoto assumed leadership of the Mizuno clan and aimed to regain control over Chita County.