Strawweight titlist Kazuto Ioka, who unified two of the major 105-pound belts with a victory against Japanese countryman Akira Yaegashi, relinquished his WBC version of the title on Sunday.
Ioka's unanimous decision against Yaegashi on June 20 marked the first time that two Japanese world titleholders had ever met to unify belts.
Ioka (10-0, 6 KOs), who entered the unification match with the WBC belt and was making his third defense, claimed Yaegashi's WBA title, which he had won in October with a 10th-round knockout of Pornsawan Porpramook in the 2011 ESPN.com fight of the year.
But with both organizations requiring the 23-year-old Ioka to make mandatory defenses, he elected to vacate the WBC version of the title.
Ioka outpointed the 29-year-old Yaegashi (15-3, 8 KOs) 115-114, 115-113, 115-113 in Osaka, Japan, but both fighters knew that the winner would have to make a decision about which belt to keep (or be stripped of one of them), because they would be unable to make two mandatory defenses at once.
To fill the vacancy, leading WBC-rated contenders Denver Cuello (31-4-6, 21 KOs) of the Philippines and Wanheng Menayothin (23-0, 7 KOs) of Thailand will be ordered to meet. Cuello had been Ioka's mandatory challenger.
Ioka could wind up vacating his remaining belt, as he has talked about moving up to the junior flyweight division.