[8] The Kojiki records Kōan was the second son of Emperor Kōshō, and that he ruled from the palace of Akitsushima-no-miya (葛城室之秋津島宮, and in the Nihon Shoki as 室秋津島宮) at Muro in what would come to be known as Yamato Province.

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

While historian John S. Brownlee calls Kōan's alleged age of 137 at the time of his death "too long", he also says that this is not unusual for mythical figures.

The Imperial Household Agency designates this location as Kōan's mausoleum, and its formal name is Tamate no oka no e no misasagi.

[13] Outside of the Kojiki, the reign of Emperor Kinmei[b] (c. 509 – 571 AD) is the first for which contemporary historiography is able to assign verifiable dates.

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