The Onmyoryo was one of the bureaus in Nakatsukasasho (Ministry of Central Affairs) under the Ritsuryo system (a system of centralized government based on the ritsuryo code). The department was responsible for the compilation of fortune-telling, astronomy, time, and calendar. It was renamed the 'Taishi department' (Bureau of Divination) between 758 and 764.
The Onmyo no Kami was the director of the bureau which was staffed by Onmyoji (yin and yang practitioners) who performed spells based on Onmyodo (way of Yin and Yang; an occult divination system based on the Taoist theory of the five elements). There was also an Onmyo Hakase (ying and yang master) who trained onmyoji, a Tenmon Hakase (master of astronomy) who practiced and taught astronomy, and a Reki Hakase (calendar master) who compiled and created calendars. Gakusei (students) and tokugyo no sho (student like postgraduate, student taking the graduate program) studied under these staff members. In addition, the Rokoku Hakase (clock master) managed the water clocks and announced the time. The Onmyoji ABE no Seimei was assigned to one of the institution's Tenmon Hakase. The Onmyo no Kami Haruo TSUCHIMIKADO passed away in 1869, and the Onmyoryo was abolished in 1870 during the time of his heir, Harenaga TSUCHIMIKADO.
1 kami (director, equivalent to Jugoinoge [Junior Fifth Rank, Lower Grade])
1 suke (deputy director, equivalent to Jurokuinojo [Junior Sixth Rank, Upper Grade])
1 jo (secretary, equivalent to Jushichiinojo [Junior Seventh Rank, Upper Grade])
1 daisakan (senior clerk, equivalent to Juhachiinoge [Junior Eighth Rank, Lower Grade]) and 1 shosakan (junior clerk, equivalent to Daihatsuinojo [Greater Initial Rank, Upper Grade])
Shisho (low-ranking clerks), newly created
Ryosho (administrative official, secretary, commissioner), newly created
20 shibu (low-ranking bureaucrats)
2 jikicho (factotums)
The followings were responsible for skills and education.
6 Onmyoji (equivalent to Jushichiinojo)
1 Onmyo Hakase (equivalent to Shoshichiinoge [Senior Seventh Rank, Lower Grade])
10 Onmyo no sho (students of onmyo)
Onmyo tokugyo no sho (top onmyo students)
1 Tenmon Hakase (equivalent to Shoshichiinoge)
10 Tenmon no sho (students of astronomy)
Tenmon tokugyo no sho (top astrology students)
1 Reki Hakase (equivalent to Jushichiinojo)
10 reki no sho (calendar students)
Reki tokugyo no sho (top calendar students)