"Shoichii (Senior First Rank)" is one of court ranks and ranks granted to Shinto gods in Japan. The highest rank among shoo (prince or imperial grandchild without an imperial proclamation, who does not descend to the status of a subject) and subjects, ranking above Juichii.
Kanpaku (chief advisor to the Emperor) and Daijo-daijin (Grand minister of state), or those who rendered distinguished service as seii taishogun (literally, "great general who subdues the barbarians") and others who accomplished great deeds for the nation were granted this rank. However, only a few in history were granted the rank in life, and most cases were conferred posthumously. Additionally, this rank was not granted after World War II, including posthumous ranks as well. Even today, although it is defined by the code for court ranks, the highest rank in fact granted is Juichii (Junior First Rank), which is one rank lower.
In principle, shinkai (ranks granted to Shinto gods) were never reduced, and unlike humans whose lives come to an end, gods have unlimited life-spans, which led to many shrines becoming Shoichii with time. Originally, shinkai were granted to shrines and were not inherited by a shrine which the enshrined deity was moved to, but with the fall of the Ritsuryo system, these shrines also carried the shinkai of their original shrines. In particular, the Fushimi Inari-taisha Shrine, the chief shrine for the Inari god, is Shoichii, and therefore, the Inari-jinja Shrines nationwide which were transferred to enshrine from there, also identify themselves as Shoichii, and 'Shoichii' has become a synonym of Inari god.