Ryan Kilpatrick “Into the Great Unknown: China's most famed explores and adventurers” that's Shanghai January 2015, pp.20-21
This time, Xu did find something. It wasn't the spring of eternal life, but it was a vast, fertile, exquiste and promising land somewhere in modern-day Japan.
Perhaps realizing that he had run out of plausible excuses (like sea monsters) for not finding the clearly non-existent potion of immortality, and that if he returned home empty-handed one more the emperor would have his head, Xu Fu did the rational thing and stayed put, setting up his own kingdom instead.
Around the same time that all this went down, Japan's ancient Jomon culture suddenly disappeared and dramatic leaps in farming techniques occurred, improving local inhabitants' quality of life and laying the foundation for ancient Japanese society. Many believe that Xu's arrival was the catalyst for Japan's development – in some parts of Japan, Xu is worshipped as the God of farming, medicine and silk. (p.21)
*3:See also http://d.hatena.ne.jp/sumita-m/20060309/1141908656 http://d.hatena.ne.jp/sumita-m/20070205/1170653400 http://d.hatena.ne.jp/sumita-m/20070227/1172599579 http://d.hatena.ne.jp/sumita-m/20090112/1231743811 http://d.hatena.ne.jp/sumita-m/20110829/1314590337
*4:See also http://d.hatena.ne.jp/sumita-m/20081219/1229651651 http://d.hatena.ne.jp/sumita-m/20110702/1309580556 http://d.hatena.ne.jp/sumita-m/20110716/1310788722 http://d.hatena.ne.jp/sumita-m/20141017/1413485324 http://d.hatena.ne.jp/sumita-m/20141116/1416157089