Former World Boxing Association super flyweight champion Tomonobu Shimizu announced his retirement on Monday, a little more than a year after he won his only title.
"Being champion of the world made me truly happy," said the 31-year-old, who defeated Mexico's Hugo Cezares in August 2011 in his third bid for a world championship.
An eye injury suffered in his victory, however, prevented him from making a mandatory defense. In April, his bid to regain the title ended in a loss to Tepparith Kokietgym of Thailand.
"I didn't feel the slightest bit of anguish," Shimizu said. "I thought that if I could take a brief respite, I would want to return, but I haven't felt that urge to give it one more try."
The native of Fukui Prefecture made his pro debut in March 2004 and finished with a record of 24-4-1 (nine knockouts). He intends to open a fitness gym in Fukui and train amateur athletes.