Naoya Inoue stopped Liverpool’s Paul Butler to become the first undisputed bantamweight champion in half a century.
Butler was the defending WBO champion but was completely outclassed by Inoue, who grew frustrated with his rival’s refusal to commit to Tokyo.
Inoue’s 21st career knockout finally came in the 11th round as he dropped Butler under a barrage of punches.
“This is the greatest moment [of my career]”, Inoue said after the fight.
It is the first time in the era of the four belts that an undisputed bantamweight champion has been crowned.
Inoue, 29, plans to move up in weight, having previously won world titles at super flyweight and lightweight.
The Japanese star was fighting in his 19th straight world title bout and remains undefeated in 24 professional fights.
Butler was aiming to be the first Englishman to become an undisputed champion in the era of four belts, but the 34-year-old returns home empty-handed after failing in his first title defense.
Inoue crosses to a historic victory
Butler had deserved applause for accepting to step into Inoue’s backyard just seven months after being promoted to WBO champion.
The Brit entered the ring for Survivor’s Eye of the Tiger but there was little bite from the traveling fighter at Ariake Arena.
Inoue moved forward in the first round, but Butler was able to catch most of his shots and spent much of his time getting away from danger.
Butler received constant instructions from his corner, which included his trainer Joe Gallagher and former world champion Scott Quigg.
Nicknamed the “Monster,” Inoue settled into a Butler-hunting rhythm. He would intermittently land quick combinations but had to work to break down Butler’s high guard.
Inoue invested in some painful body shots, but grew visibly frustrated as the fight wore on.
“Have a little swagger with you,” was Butler’s corner call, but the Briton was unable to oblige.
Inoue attempted to open Butler’s guard with a body shot before looking for a hook to the head.
The defending WBA (Super), IBF and WBC champion began pushing Butler midway through, smiling at his rival and shuffling around the ring.
Inoue invited Butler to him but was unsuccessful and produced an “Ali shuffle” in the seventh round before putting his hands behind his back in the eighth.
Inoue landed a good right hand in the ninth and the crowd offered cheers in the 10th, a rare sight in the usually quiet and respectful world of Japanese combat sports.
Inoue responded, picking up the pace quickly in the penultimate round and hurting Butler with a body shot and a left hook to the head.
Butler staggered from the force of the blows, prompting Inoue to leap forward and unload a barrage of punches, eventually dropping the Briton.
Butler couldn’t beat the count, handing Inoue a historic victory and solidifying his claim as the best fighter in the world.