Kokushi (国司, also read Kuni no tsukasa) were provincial officials in Classical Japan. They were nobles sent from the central government in Kyoto to oversee a province, a system that was established as part of the Taika Reform in 645, and enacted by the Ritsuryō system. There were four classes of kokushi, from the highest to the lowest: Kami (守), Suke (介), Jō (掾), and Sakan (目). In the Middle Ages, an acting governor called mokudai, the daikan of the kokushi, took over the local government of the province, while the kokushi returned to the capital to take on a supervising role.