Born in Fuji, Shizuoka Prefecture, Kawaguchi studied at Shimizu Commercial High School and was a member of the football team there.

Kawaguchi lost his place to veteran Dave Beasant after being held responsible for Portsmouth's 4–1 home defeat to underdogs Leyton Orient in the FA Cup.

Despite his poor performances for Pompey he remained something of a cult hero with the fans, on account of his cheerful demeanour, and his insistence that he would work hard to regain his place.

Prior to the 2005 Japanese football season, Kawaguchi returned to his home country when he signed with then-perennial title-contenders Júbilo Iwata.

A broken leg sustained in a J1 League clash against Kyoto Sanga appeared to have sidelined him for the rest of the season, thus ruling him out of the 2010 World Cup.

However, after making a full and quick recovery, Japanese head coach Takeshi Okada decided to include him in the final squad announced on 10 May 2010.