The 'Shoku' in the title of this fourth book Shoku Nihon Koki means 'continued,' so it can be seen as a direct continuation of the third book Nihon Koki (Later Chronicle of Japan), but in contrast to that third book, which covers the reigns of four emperors, and the second book Shoku Nihongi (Chronicle of Japan, Continued) which covers the reign of nine, this fourth book covers only one, Emperor Ninmyo
本書の「続日本後紀」という書名は、「日本後紀」に続くという意味であるが、「続日本紀」は九代、「日本後紀」は四代と複数の天皇の治世を対象としているのに対し本書は、仁明天皇一代の歴史である。