Under the Ritsuryo system (a system of centralized government based on the ritsuryo code), it was the highest rank granted to a queen and her female retainers. Many Daijo-daijin (Grand minister of state) (officials corresponding to Shoichii or Juichii) and kanpaku (chief advisor to the Emperor), which are Ryoge no kan (class outside of the Ritsuryo system), normally not included in the hierarchy of court ranks, were granted Juichii or Shoichii.
Additionally, later when kugyo (court noble) who could not serve as ministers were promoted to Juichii, it became a common practice that they were granted Jun-daijin (Vice Minister) by imperial proclamation.
In the Edo period, when seii taishogun (literally, "great general who subdues the barbarians") retired as ogosho and then granted Daijo-daijin, he were promoted to Juichii. Additionally, the rank was granted to the birth mother of the shogun. An example is Keishoin, the mother of the fifth Shogun, Tsunayoshi TOKUGAWA, and her title of honor was 'Ichii-sama' after being promoted to Juichii.
In the Meiji period, promotions to Juichii increased compared to the Edo period. Juichii corresponded to the first rank granted to Dukes, and those with a title of Duke or lower could be promoted to Juichii depending on their age.
There are no cases of Shoichii granted after World War II, thus, today it is virtually the highest rank as a court rank of honor. The investiture is performed by the Emperor. In kunto (Order of Merit), it corresponds to Daikuni (highest possible order of merit). For example, Prime Ministers who made distinguished achievements are granted Juichii posthumously.