He became so powerful by iron manufacturing and exploiting nearby fields and mountains, that he constructed Yogaisan Mizawa-jo (Mizawa Castle on Mt. Yogaisan) on Mt. Kamokura, later renamed to Mt. Yogaisan, in 1305, a place of strategic point which commanded a panoramic view of Nita county and also the Shimane Peninsula.
野たたら製鉄、山野開拓により力をつけ、嘉元3年（1305年）、仁多郡内をはじめ島根半島までも一望できる要衝の地・鴨倉山に当城、要害山三沢城を築城した。