Japan's Ryuya Yamanaka defended his WBO minimumweight crown for the first time on Sunday, defeating Mexico's Moises Calleros by technical knockout.

The fight was the last of two world title fights at Kobe's Portopia Hotel, where Japan's Reiya Konishi failed in his first attempt at a world title.

Calleros, the fourth-ranked contender, suffered a cut around the nose from a wicked right in the second round, and gradually got the worse of the 22-year-old champ's sharp combinations.

By the eighth round, Calleros had little fight left in him and then threw in the towel. Yamanaka, who won the title last August, improved to 16-2 with five wins by knockout. Calleros' record fell to 28-9 with one draw.

"Frankly speaking, I've never felt more relieved after a fight," Yamanaka said.

Fighting for the WBA's vacant light flyweight title, Konishi, the second-ranked contender lost a unanimous decision to Venezuela's Carlos Canizales, the No. 1 contender.

Konishi, 24, was knocked down in the third round and rallied but could not win the late rounds he needed to sway the decision. The loss was Konishi's first in 16 pro fights. Canizales improved to 20-0 with one draw.