Having gone through some difficult times, Toshiaki Nishioka's boxing career wasn't exactly what he originally thought it would be when he entered the ring at age 11.

But he now can say that it was more fulfilling than he expected.

Nishioka, who lost to Filipino Nonito Donaire in a super bantamweight world title unification match in the United States last month, announced his retirement Tuesday after spending nearly two decades as a professional fighter.