The midfielder earned 82 international caps and scored the winner in Japan's first win in the World Cup in a 1-0 victory over Russia in 2002.
Inamoto played his first match in England's top-flight league at Fulham the same year, after an underwhelming season at Arsenal. He also played for West Bromwich Albion, Cardiff City, Galatasaray, Rennes and other European clubs before returning to Japan in 2010.
"I have done it all... I have been so happy to be able to continue playing football until I'm satisfied with my life," Inamoto, who currently plays for Japanese fifth-tier side Nankatsu SC, wrote on Instagram.