Tom Johnson is the owner of Tom's Hot Dogs. He is an American from New York who, after hitch hiking around the world, decided to remain living in Japan, as such his Japanese speech is a little broken. He runs a Hot Dog stand which can usually be found in Dobuita, but sometimes he sells them at the New Yokosuka Harbor District. Tom and Ryou Hazuki have been friends for a while so he is always willing to try and help him.
Tom also has a girlfriend, Honey Jackson, who is also from America and helps him out at the hot dog stand. Her Japanese is better than Tom's, so she helps Tom by improving his speech. After Ryou is fired at the harbor job, he sees Tom during lunch where he's serving Hot Dogs at the harbor and he teaches Ryou the Tornado Kick. However, as Ryou is getting ready to leave Japan, Tom reveals that he is going back home to America.
(Source: Shenmue Wikia)