The history of the Imanishi family began when Jiro Dayu Tomasa TOCHI, born the second son of the lord of Tochi-jo Castle Minbu Dayu Totake, became the adoptive son of his father-in-law Dayu Masayuki HIGUCHI who was a shashi (chief Shinto priesthood) of Hirose-taisha Shrine whereby Jiro Dayu Tomasa became the owner of a territory over 8,000 koku where he built Kawai-jo Castle and began to refer himself as Minbu Shoyu Nakahara Tomasa KAWAI.
今西家の先祖は、十市城主民部太夫遠武の次男十市治良太夫遠正が廣瀬大社の社司樋口太夫正之の婿養子となり八千余石を領して川井城を築き川井民部少輔中原遠正と称したのが始まりである。