Court magician (方士) whom 秦始皇 sent across the eastern sea with thousands of boys and girls to find the elixir of immortality. He never came back, and legends in Japan say he settled there.
Legend says Xu Fu sailed east to Japan and never returned.
Tips
mistakes
The 史记 also writes him 徐巿. That 巿, 'leather kneecover', has a stroke running straight through its top and is not 市 'market', so 'Xu Shi' is a misreading. In Japan he is Jofuku, with a large park in his honour in Shingū, Wakayama.
A recurring motif in Chinese and Japanese historical fiction, anime, and games (e.g. Fate/Grand Order features Xu Fu as a Servant). Often invoked when discussing early China-Japan contact.