As the term "naigubu Jushi" is seen in "Shoku Nihongi" (Chronicle of Japan Continued) dated April 30, 757, the system of Jushi might have been introduced before then.
『続日本紀』天平宝字元年4月4日条（757年）に「内供奉豎子」が登場しており、設置はそれ以前に遡る。