According to some genealogies, FUJIWARA no Yorito, a remote ancestor of the Oshu Fujiwara clan, was "Taro (a word used to express the first, biggest or best things) Taihu (officers whose rank were Goi [Fifth Rank] or above), a resident of Shimousa Province," but it is not clear how and why he moved to Mutsu Province (later, Rikuchu Province).
奥州藤原氏の遠祖である藤原頼遠は諸系図によると「太郎太夫下総国住人」であったと記され、陸奥国（後の陸中国）に移住した経緯はよく分かっていない。