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 thoroughly outclassed by Inoue, who became frustrated with his rival’s refusal to engage in 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 four-belt era that an undisputed bantamweight champion has been crowned.
Inoue, 29. plans to move up in weight, having already won world titles at super-flyweight and light-flyweight.
The Japanese star was fighting in his 19th world championship bout in a row and remains undefeated in 24 professional fights.
Butler was aiming to be the first Englishman to become an undisputed champion in the four-belt era, but the 34-year-old returns home empty-handed having been unsuccessful in the first defence of his title.
Inoue cruises to historic win
Butler had earned plaudits for agreeing to travel to Inoue’s backyard just seven months after being upgraded to WBO champion.
The Briton entered the ring to Survivor’s Eye of the Tiger but there was little bite from the travelling fighter at the Ariake Arena.
Inoue pressed forward from the first round, but Butler was able to catch most of his punches and spent much of his time circling away from danger.
Butler was getting constant instruction from his corner, which included his trainer Joe Gallagher and former world champion Scott Quigg.
Nicknamed the ‘Monster’, Inoue settled into a rhythm of hunting Butler down. He would intermittently land quick combinations but needed to work to break down Butler’s high guard.
Inoue invested in painful body shots, but became visibly frustrated as the fight grew on.
“Have a bit of swagger to you,” was the call from Butler’s corner, but the Briton was unable to oblige.
Inoue tried to open Butler’s guard with a body shot before searching for a hook to the head.
The reigning WBA (Super), IBF and WBC champion began to goad Butler at the midway point, smiling at his rival and shuffling round the ring.
Inoue invited Butler on to him but with no success 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 encouragement in the 10th, a rare sight in the usually quiet and respectful Japanese combat sports world.
Inoue responded, rapidly increasing the pace in the penultimate round and hurting Butler with a body shot and left hook to the head.
Butler staggered from the force of the blows, prompting Inoue to surge forward and unload a barrage of punches, finally dropping the Briton.
Butler was unable to beat the count, handing Inoue a historic win and strengthening his claim as the world’s best fighter.
Panamanian Enrique Pinder was the last undisputed bantamweight champion in 1972.
