Using the pretext of hunting down the Taira family, Yoritomo was defeated at the Battle of Ishibashiyama, and upon escaping to Boso, the estate of his ally Tsunetane CHIBA, he was brought together with the orphan of Mutsu Rokuro Yoshitaka.
頼朝、平家追討の旗を挙げ、石橋山の合戦にて敗れ房総に落ち延びた折、味方に参じた千葉常胤の屋敷にて、かの陸奥六郎義隆の遺児を引き合わされた。