Along with the "Teishinko-ki," the diary of his father FUJIWARA no Tadahira, and "Rihoo ki," the diary of Shikibu-kyo (the Highness of Ceremonial), Imperial Prince Shigeakira, it is an important historical source for knowing the political history of the mid-Heian period.
父藤原忠平の日記『貞信公記』や、式部卿重明親王の日記『吏部王記』等とともに、平安時代中期の政治史を知る上での一級史料である。