In 1379 Yorimoto's older brother Yoriyuki HOSOKAWA was overthrown in a coup d'etat, the Koryaku Coup, whereupon Yorimoto departed for the island of Shikoku with Yoriyuki but, during the following year, Yoriyuki was pardoned by the shogun Yoshimitsu ASHIKAGA and, in 1391 there was a shift in the post of kanrei (shogunal deputy) from Yoshimasa SHIBA whereupon Yoriyuki took control.
1379年(康暦元/天授(日本)5)に、管領である兄の細川頼之が斯波氏を中心とするクーデター・康暦の政変で失脚すると、兄とともに四国へ下るが、翌年に頼之が将軍足利義満から赦免されると1391年（明徳2/元中7）に斯波義将に代わり管領となる。