Among several branches of the Mitoya clan, the most famous one is the Mitoya clan, which claimed descent from a branch of Seiwa-Genji (the Minamoto line descended from Emperor Seiwa), a MINAMOTO no Mitsuyoshi line, Shinano Genji, and which bore the name of Mitoya after they settled in Izumo Province.
清和源氏源満快信濃源氏一族を称した三刀屋氏が有名で、この一族は出雲国に住した後に三刀屋を名字とする。