This 'Yasutomi-ki' shows parts which both the current "Oshu Gosannen Ki" and "Gosannen Kassen Ekotoba" are lacking, for example, the death of KIYOHARA no Sanehira and the process of the conflict between FUJIWARA no Kiyohira and his younger maternal half-brother KIYOHARA no Iehira after that.
現存する『奥州後三年記』『後三年合戦絵詞』ともに欠けている部分、例えば清原真衡の死と、その後の藤原清衡と異父弟・清原家衡の衝突の経緯などを、この「康富記」から知ることが出来る。