Daijō-daijin
The Daijō-daijin or Dajō-daijin (太政大臣, Chancellor of the Realm) was the head of the Daijō-kan (Department of State) in Heian Japan and briefly under the Meiji Constitution.
Emperor Tenji's favorite son, Prince Ōtomo, was the first to have been accorded the title of Daijō-daijin during the reign of his father. The Asuka Kiyomihara Code of 689 marks the initial appearance of the Daijō Daijin in the context of a central administrative body composed of the three ministers: the Daijō Daijin (Chancellor), the Sadaijin (Minister of the Left), and the Udaijin (Minister of the Right). These positions were consolidated under the Code of Taihō in 702.
The Chancellor presided over the Great Council of State, and controlled the officers of the state, in particular the Sadaijin and Udaijin, as well as four great councillors and three minor councillors. The ministers in turn controlled other elements of the government.
As the Fujiwara clan—which dominated the regency—gained influence, the official government offices diminished in power. By the 10th century, chancellors had no power to speak of unless they were simultaneously regent, or otherwise supported by the Fujiwara. Although the position continued in name until 1885, by the beginning of the 12th century, the office was essentially powerless, and was often vacant for lengthy periods. Substantial administrative power over the government was in other hands.