It is believed that Yoritane CHIBA lost his political backup as the peace was concluded between the Muromachi bakufu and Shigeuji ASHIKAGA in 1482 and Dokan OTA was killed four years after that, and he eventually died in 1493 having lost control over Shimosa Province.
文明14年（1482年）の室町幕府と足利成氏の和議、その4年後に太田道灌が殺害されると、千葉自胤は政治的な後ろ盾を失って下総における支配を失ったまま明応3年（1493年）の死去に至ったと推定される。