In 1445, at 16 years of age, he became a kanrei (a shogunal deputy) and took over from Mochikuni (Tokumoto) HATAKEYAMA; from that point onward, he continued to influence the shogunate administration by serving as a kanrei at three different times for a total of 23 years.
文安2年（1445年）、畠山持国（徳本）に代わって16歳で管領職に就任すると、以後3度に渡って通算23年間も管領職を歴任し、幕政に影響力を及ぼし続けた。