Emperor Kōan

was the 6th emperor of Japan, according to the traditional order of succession. Historians consider Emperor Kōan to be a legendary person; and the name Kōan"-tennō" was created for him posthumously by later generations.
No certain dates can be assigned to this emperor's life or reign. The conventionally accepted names and sequence of the early emperors were not to be confirmed as "traditional" until the reign of Emperor Kammu, who was the 50th monarch of the Yamato dynasty. 
The "Gukanshō" ruled from the palace of "Akitsushima-no-miya" at Muro in what will come to be known as Yamato province. 
Traditional history.
Kōan is almost certainly a legend. The "Kojiki" records only his name and genealogy. The "Nihonshoki" includes Kōan as the fifth of .
Emperor Kōan was the second son of Emperor Kōshō. "Jinnō Shōtōki" records that his mother was Yosotarashi-no-hime, who was the daughter of Okitsuyoso, and ancestress of the Owari.
Events of Kōan's life.
The absence of information about Kōan does not imply that no such person ever existed. Very little information is available for study prior to the reign of the 29th monarch, Emperor Kimmei. 
After his death.
This emperor's official name after his death (his posthumous name) was regularized many centuries after the lifetime which was ascribed to Kōan. 
The actual site of his grave is not known. According to the Imperial Household Agency, this emperor is venerated at a memorial Shinto shrine ("misasagi") at Nara.