"Gyokuyo" is a diary of Kanezane KUJO, who was Kanpaku (chief adviser to the Emperor) and Daijo-daijin (Grand minister of state). It is also called "Gyokukai" or "Tsukinowa Kanezaneko Ki." It is a record of public and private matters by Kanezane, who was in the position of Kanpaku in the era of great transition from the Imperial Court to samurai government.
Descriptions cover a period from 1164 to 1200. Diaries of court nobles had a purpose to pass down traditional practices of court functions, etc. to future generations and, therefore, procedures of ceremonies are described in detail.
Also, it contains many descriptions of the Jisho-Juei War in that period, and it became a basic historical material of the era, from the end of Heian period to the beginning of Kamakura period. Other historical sources of the same era include "Azuma Kagami." As it was edited from the standpoint of the Hojo clan of the Kamakura bakufu (Japanese feudal government headed by a shogun) and is close to an official history, it is used along with and to complement "Gyokuyo," which was described as a diary of a person on the Royal Court side.
After the death of Michiie KUJO, who was a grandson of Kanezane, the original was passed down in the Ichijo family, the manuscript copy was passed down in the Kujo family. Reportedly, although the name "Gyokuyo" was not used by the Nijo family, "Gyokukai" was used.