| King of Wa | |
| Predecessor: | Chin of Wa |
| Successor: | Ko of Wa |
| Issue: | Ko of Wa, Bu of Wa |
| Posthumous Name: | Emperor Ingyo? |
Sai of Wa (済) was a king of Wa in the middle of the 5th century (Kofun era). He was also known as Wa Osai.
Father of Ko and Wu, he was one of the Wa. He is considered to be the 19th Emperor Ingyo.
In the History of the Southern Dynasties, the article on the Japanese Kingdom (Nan shi wagu den) describes the contents of the Song Shu Chronicles.
In the article in the Sung Shu, Je takes the surname "Wa" (倭) as did the previous Japanese king Jin, but does not clarify his relationship to Jin. Since they do not name the continuation, there is a theory that Je and Chin were not close blood relatives, and since the Nihon Shoki shows a struggle in the succession to the throne after Emperor Nintoku, the possibility of the existence of such a struggle over the throne is pointed out In addition, since the can be seen as a particularly powerful royal family in the Chin period, there is a theory that there were two royal forces at that time (Mozu Kofun Cluster and Furuichi Kofun Cluster), and that Je may have been a lineage of this Wazui 。
During the period of activity of the Five kings of Wa, the tombs of the great kings were constructed in the Mozu Tombs and Furuichi Kofun Cluster (Osaka Prefecture, Sakai City, Habikino City, Fujiidera), and Je's tomb is assumed to be one of them.[2] These tombs are now designated as mausoleums by the Miyouchi Agency, so there is a lack of archaeological data to date them, but one theory compares them to the Ichinoyama Kofun (the current imperial tomb of Emperor Ingyo).
Another archaeological source is the excavated from the (Ichihara City, Chiba Prefecture). (or Chin), since he is self-explanatory only by writing "Wang". It should be noted, however, that the iron sword from Inariyama burial mound inscription and the inscription are distinct from the "Great King" of the Inariyama Sword。