It seems that Kagemori was on the outs with the second shogun MINAMOTO no Yoriie who had succeeded to Yoritomo after his death, and in "Azuma Kagami" (The Mirror of the East), there is the first appearance of article about Kagemori which describes an incident that Kagemori was saved by Masako HOJO, a widow of Yoritomo, when Yoriie took Kagemori's favorite concubine and tried to conduct chusatsu (kill a criminal) of Kagemori in 1199 soon after the period of Yoriie started.
頼朝死後に跡を継いだ2代将軍源頼家と景盛は不仲であったと見られ、頼家の代となって間もない正治元年（1199年）、景盛が頼家から愛妾を奪われ誅殺されようとした所を、頼朝未亡人北条政子に救われるという事件が『吾妻鏡』の景盛の記事初見に見られる。