Emperor Kaika

is the 9th emperor of Japan, according to the traditional order of succession. Historians consider Emperor Kaika to be a legendary person; and the name Kaika"-tennō" was created for him posthumously by later generations.
No certain dates can be assigned to the 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" records that Kaika ruled from the palace of "Isakawa-no-miya" at Kasuga in what will come to be known as Yamato province.
Traditional history.
Kaika is almost certainly a legend. The "Kojiki" records only his name and genealogy. The "Nihonshoki" includes Kaika as the eighth of .
Kaika was the second son of Emperor Kōgen.
Some scholars question the existence of the first nine emperors. These critics consider Kōgen's son (Suijin) to be the earliest to have actually existed.
Events of Kaika's life.
The absence of information about Kaika 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 Kaika. 
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") in Nara.