To compensate for the disappearance of the "Nihonkoki" (Later Chronicle of Japan), the "Nihon isshi" describes the period between 792 and 833 in chronological order by introducing episodes featured in books such as "Ruiju kokushi" (Assorted national histories), "Nihongi Ryaku" (Summary of Japanese Chronologies), "Ruiju sandai kaku" (Assorted regulations from Three Reigns), and "Seiji Yoryaku" (Brief Outline of Government) as exact excerpts of original texts.
『日本後紀』の欠をおぎなうべく、『類聚国史』、『日本紀略』、『類聚三代格』、『政事要略』その他の記事を、延暦11年以降天長10年まで、原文のまま、編年体で記述する。