Is the Tenno from Korea?
[From Samguk yusa] Historical Record of the Three Kingdoms, 1146, compiled by the historian Kim Pusik in the twelfth century
In the fourth year of King Adalla [158 AD], there lived on the east coast a couple named Yôno and Seo. One day the husband went to the sea to gather seaweed. Suddenly a rock, or a fish, carried him off to Japan. The people there thought him extraordinary and made him their king. Wondering why her husband did not come back, Seo searched for him and found a pair of shoes on a rock. No sooner had she climbed on the rock then it carried her away to Japan. The Japanese saw it, thought it strange, and reported the matter to the king. The couple was thus reunited. At this time, the sun and moon lost their light in Silla. The astrologer divined that the spirits of the sun and moon had left Silla for Japan, thereby causing the strange phenomenon. King Adalla then sent an envoy to Japan to find the couple. Yôno declared, "My coming to this country must be a wish of Heaven. How can I leave? Here is a roll of fine silk cloth woven by my wife. Take it home and offer it as a sacrifice to Heaven. Everything will be all right again." The envoy reported the matter to the king, who offered the sacrifice to Heaven. As expected, the sun and moon shone again. The king placed the silk cloth in his storehouse-- called Kwibigo, or the Queen's Storehouse-- as a national treasure. The place where he worshipped Heaven was named Yôngil, Welcoming the Sun, or Togiya, The Field of Prayer.