There is a possibility that Keikō actually lived or reigned in the 4th century AD rather than the 1st, but more information is needed to confirm this view.

Accounts in the Kojiki and Nihon Shoki are split when it comes to initial territorial expansion during Emperor Keikō's reign.

In the Kojiki, the Emperor is said to have sent his son "Prince Ōsu" (Yamato Takeru) to Kyūshū to conquer local tribes.

[10] The possessions of the dead prince were gathered together along with the sword Kusanagi; and his widow venerated his memory in a shrine at her home.

[12] His name might have been regularized centuries after the lifetime ascribed to Keikō, possibly during the time in which legends about the origins of the imperial dynasty were compiled as the chronicles known today as the Kojiki.

The consecutive reigns of the emperors began to be compiled in the 8th century, and it is thought that age gaps were "filled up" as many lacunae were present.

While the actual site of Keikō's grave is not known, the Emperor is traditionally venerated at a memorial Shinto shrine (misasagi) at Nara.

The Imperial Household Agency designates this location as Keikō's mausoleum, and is formally named Yamanobe no michi no e no misasagi.

Unless otherwise noted (as BC), years are in CE / AD  * Imperial Consort and Regent Empress Jingū is not traditionally listed.