Emperor Sujin
Like Emperor Kōshō and Emperor Kōrei, there is a possibility that "Kaika" could have lived instead in the 1st century (AD). Historian Louis Frédéric notes this idea in his book "Japan Encyclopedia" where he says "more likely early AD", but this remains disputed among other researchers. The first emperor that historians state might have actually existed is Emperor Sujin, the 10th emperor of Japan. Outside of the Kojiki, the reign of Emperor Kinmei ( – 571 AD) is the first for which contemporary historiography is able to assign verifiable dates. The conventionally accepted names and dates of the early Emperors were not confirmed as "traditional" though, until the reign of Emperor Kanmu between 737 and 806 AD.