Its original responsibility was to take care of the emperor's archives and imperial documents as well as to attend to various personal needs of the sovereign. However, over the course of the 9th century, the office's role and responsibilities expanded considerably, and by the end of the 9th century it had become a clear control point within the government.
Initially, this office was responsible for managing the emperor's personal belongings and documents, but over time, its responsibilities increased substantially, until it became an essential hub of power within the government by the end of the 9th century.