Emperor Seinei

Emperor Seinei (清寧天皇, Seinei-tennō) (444 – 484) was the 22nd (possibly legendary) emperor of Japan, according to the traditional order of succession. He is best known for events that took place before and after his reign with a void in between. These include a rebellion which was quickly put down, and a succession crisis as the Emperor had no children. Because Seinei had such a low profile, historians have questioned his existence and whether he ever ascended to the throne.

No firm dates can be assigned to this emperor's life or reign, but he is conventionally considered to have reigned from 480 to 484. Dates confirmed as "traditional" did not appear until the reign of Emperor Kanmu (the 50th emperor). Modern historians have come to the conclusion that the title of "Emperor" and the name "Seinei" were used by later generations to describe him.

Source: Wikipedia — https://en.wikipedia.org/wiki/Emperor_Seinei