The fact that the five kings of Wa (ancient name of Japan) in the 5th century called themselves 'Wasan,' 'Wasai,' and so on, can be seen in "Sosho" Wakokuden (articles about Wa written in Sung) and Bunteiki, and it is clear that the kings at that time had the family name of 'Wa.'
5世紀の倭の五王が、倭讃、倭済などと称したことが『宋書』倭国伝ないし文帝紀などに見え、当時の倭国王が「倭」姓を称していたことがわかる。