Shoshii was divided into Upper and Lower under the Ritsuryo system (a system of centralized government based on the ritsuryo code), and it ranked below Jusanmi (Junior Third Rank) and above Jushii (Junior Fourth Rank). Under the Ritsuryo system, it was divided into Jushiinojo (Junior Fourth Rank, Upper Grade) and Jushiinoge (Junior Fourth Rank, Lower Grade). In kunto (Order of Merit), it corresponds to Kunyonto (Fourth Class of Order), and Kami (director) and Suke (assistant director) of government officials in Kyoto such as Sakyo no daibu (Master of the Eastern Capital Offices) and Ukyo no daibu (Master of the Western Capital Offices) who perform administration in the Imperial Court corresponded to this court rank.
The title of honor for those ranked Jushiinoge or higher and Shoshiinojo (Senior Fourth Rank, Upper Grade), and who were not listed as kugyo (court noble) was basically Nanori Ason, in which Ason (second highest of the eight hereditary titles) was added under their family names or imina (real name).
For example, 'Hosokawa Ukyo no daibu Jushiinoge MINAMOTO no Katsumoto Ason.'
Under the Ritsuryo system where Sanmi or higher was considered kugyo, many of the collateral family members of the Fujiwara clan and non-Fujiwara clan middle class nobles held the court rank, Shii. When the starting rank was Jugoinoge (Junior Fifth Rank, Lower Grade) and the highest rank was Shoshii for the leading samurai, Seiwa-Genji (Minamoto clan) and Kanmu Heishi (Taira clan), even those in the lineage of eldest son were not promoted unless there were some deeds of arms.
However, in the Kamakura period, since the Hojo clan, who gained power since the Kamakura bakufu (Japanese feudal government headed by a shogun) was established and succeeded in exterminating their political enemies, seized shikken (regent for shogun) posts in the bakufu, those in the lineage of eldest son in the Hojo clan began being promoted to Shoshiinojo, and Hojo clan members and powerful gokenin (an immediate vassal of the shogunate in the Kamakura and Muromachi through Edo periods) were promoted to court ranks such as Jushiinoge. Furthermore, from the Muromachi period onward, it was granted to dominant Shugo daimyo (Japanese territorial lord as provincial constable). In particular, the Ashikaga clan, who served as sankanrei shishiki (three families assigned as assistants of shogun and four families serving as director of samurai-dokoro (Board of Retainers)), and dominant Shugo (provincial constable), or noble shugo families were granted the Jushiinoge.
Additionally, in the Ashikaga shogun family, court ranks such as Gon Dainagon (provisional major counselor), which were equivalent to kugyo, were the starting ranks, but in the late Muromachi period, conflict occurred within the Ashikaga shogun family over who would succeed as shogun, and the 13th Shogun, Yoshiteru ASHIKAGA, Yoshiaki ASHIKAGA, etc., became seii taishogun (literally, "great general who subdues the barbarians") as Jushiinoge, and there were cases where they were listed as kugyo while being Jushii, without becoming Shoshii.
In the Sengoku Period (Period of Warring States), the Miyoshi clan, who were a vassal of sankanrei Hosokawa clan and a family of Shugodai (deputy of Shugo, provincial constable), were listed as Shobanshu (officials who accompany the Shogun) of the bakufu and were granted Jushiinoge, and this led to their vassal, Hisahide MATSUNAGA, also being promoted to Jushiinoge like his master family, and appointments were made according to real abilities rather than parentage or social status.
When Hideyoshi TOYOTOMI conquered the country as a successor to Nobunaga ODA, who overthrew the Muromachi bakufu, but died a violent death with the conquering of the country in sight, Hideyoshi advanced to kanpaku (chief advisor to the Emperor), while chief vassals such as Ieyasu TOKUGAWA and Toshiie MAEDA were granted Nii (Second Rank) and Sanmi (Third Rank), and Jushii began being issued as court ranks for their legitimate children and chief vassals.
Additionally, when Ieyasu established the Edo bakufu, kamon daimyo (feudal lords who are relatives of the shogun, but neither sanke (three families of the Tokugawas) nor sankyo (three Tokugawa clan families who separated from the clan)) and fudai daimyo (a daimyo in hereditary vassal to the Tokugawa family) who held executive positions such as roju (member of shogun's council of elders, koke (privileged family under Tokugawa Shogunate), tozama daimyo (nonhereditary feudal lord) who were daimyo of 100,000 koku or more, were granted this court rank.
Currently, the court rank is issued to the deceased who made achievements, and is granted to government workers who made achievements, university professors with achievements in performing arts, cultural activities, academic research, etc.