According to Daijokanpu (official documents issued by the Grand Council of State) issued on June 9, 820, the reason for the reestablishment of Naiju was because the number of Otoneri (Imperial Attendant) was halved from 800 persons ("Ruiju sandai kaku" (Assorted regulations from Three Reigns)).
なお、弘仁11年4月21日（820年6月5日）の太政官符には、内豎の復置を理由に大舎人を800名から半減することが書かれている。（『類聚三代格』）、