-571 AD ) , the 29th emperor , is the first for which contemporary historiography is able to assign verifiable dates ; however , the conventionally accepted names and dates of the early emperors were not to be confirmed as `` traditional '' until the reign of Emperor Kammu ( 737-806 ) , the 50th sovereign of the Yamato dynasty .
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 .