Udaijin in the context of "Taihō Code"

Wake no Kiyomaro (和気 清麻呂; 733–799) was a high-ranking Japanese official during the Nara period. He was born in Bizen Province (now Wake, Okayama) to a family of politically important, devoted Buddhists who hoped to keep Buddhism and politics separate through religious reform. He became a trusted advisor to Emperor Kanmu, a position which he used to encourage the development of Buddhism in a direction which would prevent it from posing a threat to the government. According to the Shoku Nihongi, he was sent to the Usa Shrine to receive a divine message; stating that only those of descent from Amaterasu could become emperor, it refuted the previous divine message claiming Dōkyō was to be the next emperor after Empress Kōken (later Empress Shōtoku). This report angered Dōkyō, who used his influence with the Empress to have an edict issued sending Kiyomaro into exile; he also had the sinews of Kiyomaro's legs cut, and only the protection of the Fujiwara clan saved him from being killed outright.

The following year, however, Empress Shōtoku died. She was succeeded by Emperor Kōnin, who in turn exiled Dōkyō to Shimotsuke Province and not only recalled Wake no Kiyomaro from exile, but also appointed him as both kami (governor) of Bizen Province and Udaijin (junior minister of state). The following year, he petitioned the governor of Dazaifu to send officials to Usa to investigate allegations of "fraudulent oracles"; in his later report, Wake no Kiyomaro stated that out of five oracles checked, two were found to be fabricated. This resulted in the government relieving Usa no Ikemori of his position as head priest and replacing him with the previously-disgraced Ōga no Tamaro. Following this, Wake no Kiyomaro returned to Yamato. He remained a trusted advisor to Emperor Kammu; in the spring of 793, he convinced the emperor to abandon the delay-plagued construction of a capital at Nagaoka and instead seek another location to the northeast, at Heian-kyō (modern-day Kyōto.

The Daijō-kan or Dajō-kan (Japanese: 太政官), also known as the Great Council of State, was (i) (Daijō-kan) the highest organ of Japan's premodern Imperial government under the Ritsuryō legal system during and after the Nara period or (ii) (Dajō-kan) the highest organ of Japan's government briefly restored to power after the Meiji Restoration, which was replaced by the Cabinet. In Yamato name it is also called "Ōmatsurigoto-no-Tsukasa" 於保伊萬豆利古止乃官）.

It was consolidated in the Taihō Code of 702. The Asuka Kiyomihara Code of 689 marks the initial appearance of this 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).

The Asuka Kiyomihara Code (飛鳥浄御原令, Asuka Kiyomihara-ryō) refers to a collection of governing rules compiled and promulgated in 689, one of the first, if not the first collection of Ritsuryō laws in classical Japan. This also marks the initial appearance of the central administrative body called the Daijō-kan (Council of State) composed of the three ministers—the Daijō-daijin (Chancellor), the Sadaijin (Minister of the Left) and the Udaijin (Minister of the Right).

In 662, Emperor Tenji is said to have compiled the first Japanese legal code known to modern historians. The Ōmi-ryō, consisting of 22 volumes, was promulgated in the last year of Tenji's reign. This legal codification is no longer extant, but it is said to have been refined in what is known as the Asuka Kiyomihara ritsu-ryō of 689. The compilation was commenced in 681 under Emperor Tenmu. The Emperor died in 686, but the finalization of the Code took a few more years. It was promulgated in 689. These are understood to have been a forerunner of the Taihō ritsu-ryō of 701.