Satoh (whose real first name is Takahiko and I don't know why he's called "G.G." - UPDATE: Now I do. See below) is one of the few Japanese players to have signed with a US team out of college. In his case, the Phillies signed him after he graduated from Hosei in 2000. He spent three years in the Phillies organization, rising as high as their Low-A team in Lakewood, NJ (in the South Atlantic League). He had been an infielder in college but the Phillies decided that his strong arm would be best used as a catcher. His first baseball cards are minor league issues from the US - the 2001 and 2002 Batavia team sets and the 2003 Lakewood team set.
I'm not entirely sure why and how he left the Phillies, but there aren't many 24 year olds who hit .247 with little power in the Low-A ball who go on to be major league players (especially catchers who only throw out 23% of base stealers) so I suspect that the Phillies released him. He returned to Japan and was drafted by the Seibu Lions in the seventh round of the fall 2003 draft. (I initially thought that he did not have a card in the 2004 BBM Rookie Edition set but it turns out his card is labelled "Takahiko" rather than "GG".)
He played sparingly with the ichi-gun Lions team his first couple years but he became the Lions regular right fielder in 2007. He hit .280 with 25 home runs that year and followed it up by hitting .302 with 21 home runs in 2008 and .291 with 25 home runs in 2009. He was the top vote getter for the All Star games in 2008, the only time he made the team. He was the starting left fielder for Team Japan in the Olympics that year and made a key error in the bronze medal game against the US that lead to the US team making a comeback and winning the game. The Lions won the Nippon Series that year but Satoh missed the post-season due to injury.
His numbers dipped substantially in 2010 and he was demoted to ni-gun halfway through the season. He had shoulder surgery late in the season and spent all of 2011 in the minors. The Lions released him at the end of the season.
He spent 2012 playing for Fortitudo Bologna of the Italian Baseball League and then briefly joined the Roki Techno industrial league team. Before he could play a game for them, however, the Marines signed him. He only appeared in 30 games with the top team in 2013 and he spent all of 2014 with the ni-gun team. He was released by Lotte at the end of the season and apparently decided to retire.
Here's a selection of his cards:
|2004 BBM 1st Version #61|
|2006 BBM Lions #L073|
|2008 BBM All Stars #A63|
|2008 BBM Japan National Team #JPN28|
|2010 BBM Lions 60th Anniversary #99|
|2013 BBM 1st Version #291|
|2013 BBM Marines #M90|
UPDATE: Got an email from Larry Fuhrmann that said that "Jiji is Japanese slang for grandpa. So I guess even at a relatively young age, his teammates thought he looked like an old man. And since Satoh is a very common surname in Japan, like Smith or Jones in America, he decided to spice up and stylize his name to stand out from all the other Satohs, so he started to call himself G.G. Satoh."
Thanks for the explanation, Larry!