斎藤氏
In 1444, Sōen killed Mino Province's "shugodai" from the Tomishima clan (富島氏 "Tomishima-shi") and started a civil war within the province. To support his father, Toshinaga built Izumii Castle to serve as the base for the Saitō clan. When Sōen was assassinated in 1450, Toshinaga assumed control of the clan and became the "shugo" of the province.