Japan's WBO super flyweight champion Naoya Inoue and WBC light flyweight champion Ken Shiro both easily retained their titles on Saturday.
Inoue demolished France's Yoan Boyeaux in a third-round technical knockout to improve to 15-0 in his career with his 13th career knockout. Ken Shiro, whose real name is Kenshiro Teraji, improved to 12-0 in a fourth-round TKO of Panama's Gilberto Pedrozo at Bunka Gym in Yokohama.
Boyeaux, who hadn't lost a fight since January 2012, had no answers for a series of punishing left-handed body blows from Inoue, who was defending his title for the seventh time.
"My left has been a strength of mine," said Inoue who said he would seek either a super flyweight unification title or perhaps try moving up a class to bantamweight.
"I have a lot of options. I'm looking forward to something new, including maybe a new start as a bantamweight."
Boyeaux's record fell to 41-5.
Earlier, Ken Shiro made short work of Pedrozo. The Japanese champ kept his opponent from coming close enough to land some ferocious right crosses, started cautiously with left jabs before landing combinations as the second round came to a close.
Pedrozo was staggered in the fourth round and was given a standing eight count before Ken Shiro was quickly on him again, forcing the referee to stop the fight.
"Normally, I'm a slow starter," Ken Shiro said. "I wanted to up the tempo a little bit. I just tried to apply whatever pressure I could."
Ken Shiro's sixth career win by knockout left Pedrozo with an 18-4 record.