Analysis of information sources in references of the Wikipedia article "Emperor Kōan" in English language version.
Posthumous names for the earthly Mikados were invented in the reign of Emperor Kanmu (782–805), i.e., after the date of the compilation of the Records and the Chronicles.
According to legend, the first Japanese Emperor was Jimmu. Along with the next 13 Emperors, Jimmu is not considered an actual, historical figure. Historically verifiable Emperors of Japan date from the early sixth century with Kimmei.