Further, from the fact that Soen's wife was a daughter of Masataka MASHIKO and that Soen's heir Munetsuna assumed the family name Hatta, Soen is likely to have extended power over not only Shimotsuke Province but also in the vicinity of the Western part of Hitachi Province (in the vicinity of Shimodate City, Ibaraki Prefecture), supposedly keeping the Haga, Mashiko and Hatta clans under control.
その他、室が益子正隆の娘であったことや、次代宗綱が八田姓とされる点などから、その勢力は下野国のみならず常陸国西部付近（茨城県下館市付近）にも達しており、芳賀氏、益子氏、八田氏をその勢力下に置いていたと推定されている。