Sogo refers to the profession of Sokan (official positions given to Buddhist priests by Imperial Court) to manage Buddhist priests and nuns in Japan.
In the Ritsuryo system (a system of centralized government based on the ritsuryo code), it was under the control of Genba-ryo (diplomacy and Buddhism Office). It consists of Sojo (the highest rank Buddhist priest), Sozu (the second highest rank Buddhist priest) and Risshi (the third rank Buddhist priests), with Sakan (clericals) to support them.
It was established in 624, and it served an important role in the Buddhism world under the Ritsuryo system. Sogosho as its office was located in Yakushi-ji Temple in the Nara Period, and in Sai-ji Temple after the transfer of national capital to the city of Heian-kyo.
In 819, the fixed number of Sogosho was determined as one Sojo, one Daisozu (the highest grade that can be held by one who has reached the second highest rank in the hierarchy of Buddhist priests), one Shosozu (the lower grade Buddhist priests of Sozu) and four Risshi.
In 864, Soi as the official rank of Sogo was determined to give Hoin daiwajo-rank to Sojo, Hogen wajo-rank to Sozu and Hokkyo shonin-rank to Risshi.