According to the "Kanshoku Hisho" (a text describing rules of ceremony and etiquette to be observed in the imperial court and by samurai that was written during the early Heian period in around 1200), "Shokugensho" (A book on Japanese government officials written by Chikafusa KITABATAKE), "Hyakuryo Kunyosho" (practical guide on Yusoku kojitsu [court and samurai rules of ceremony and etiquette]) and so on, it was described that increasingly, Daibu, who would become Kami (director) for years to come, was selected from Shii (Fourth Rank) and Suke, the assistant director, from Rokui (Sixth Rank) conversely.
『官職秘抄』や『職原鈔』、『百寮訓要抄』などによると、後世には長官である大夫は四位から、逆に次官である亮は六位から選ばれる例が多くなった事が記されている。