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He was the eldest son of Haruhisa and he was given the childhood name of Saburōshirō (三郎四郎). After his father's sudden death in 1560, he became the head of the clan to continue the fight against the Mōri clan. While besieged in Toda Castle, Yoshihisa had a retainer, Moriyama Hisakane executed after fearing betrayal. This caused most of his remaining troops to desert and on 1566, he surrendered to Mōri Motonari. Yoshihisa was permitted to become a monk and was held captive at Enmeiji. With the head of clan gone, the members of the Amago clan were forced to serve as retainers to other daimyo.
As a monk, Yoshihisa changed his name to Yurin(友林). After Mōri Terumoto became the head of Mōri clan, he became a retainer under Terumoto.