Kesshi-Judai (Ten Undocumented Sovereigns) (欠史十代)
Kesshi-Judai refers to the ten Emperors from the twenty-fourth Emperor Ninken to the thirty-third Empress Suiko, who only have their genealogy and not their achievements recorded in "Kojiki" (The Records of Ancient Matters), or to this period of time.
Unlike Kesshi-Hachidai (Eight Undocumented Sovereigns), the achievements of these ten Emperors are recorded in "Nihonshoki" (Chronicles of Japan), but not in "Kojiki." The period of these ten Emperors falls into the last period covered by "Kojiki."
There are various opinions about the differences in historical description between "Kojiki" and "Nihonshoki." Various theories have been put forward about why Nihonshoki provides a detailed description about Prince Shotoku while "Kojiki" contains only his genealogy, suggesting that there must be some meaning to the difference itself.
One theory is that the eighth century Japanese writers who penned "Kojiki" (= a book about the ancient period) believed that the true 'ancient times' ended with the twenty-third Emperor Kenzo and the 'early modern times' more closely related to themselves started with the thirty-third Empress Suiko, so the period in between was written in such a method to express this transition.