LAS VEGAS (AFP) — Unbeaten Naoya Inoue of Japan retained his undisputed super bantamweight world crown on Sunday, climbing off the canvas to stop American Ramon Cardenas in the eighth round in Las Vegas.

Inoue improved to 30-0 with his 27th victory inside the distance when referee Thomas Taylor halted the fight 45 seconds into the eighth round after a flurry of powerhouse punches by the champion with Cardenas only able to cover up.

"Watching the fight, everybody is very much aware I like to brawl," Inoue said.

Inoue was knocked down for only the second time in his career, by a left hook from the heavy underdog in the second round, but the champion adjusted and pressed the attack from there.

"I was very surprised but I was able to calmly pull myself together," Inoue said through a translator.

"In the first round, I thought I had pretty good distance but in the second round it kind of got a little loose. And then from then thereafter I made sure I didn't take that punch again."

The 32-year-old Japanese star nicknamed "The Monster" defended his undisputed world title in the 122-pound (55.3kg) division for the fourth time.

The fight marked his return to Las Vegas for the first time in four years, Inoue fighting outside Japan for the first time since 2021.

Inoue was coming off a fourth-round knockout of South Korea's Kim Ye-joon in Tokyo in January.

Inoue has not been taken to the 12-round maximum distance in a fight since a 2019 unanimous-decision victory over Filipino Nonito Donaire, having won 11 fights since.

Cardenas, 29, fell to 26-2 but made a game effort in his first world title fight.

"Odds-wise he was really far apart but I knew he was tough," Inoue said.

"Boxing is not that easy."

Cardenas knocked down Inoue in the final seconds of the second, the Japanese star landing on his rear and quickly getting to his knees and rising just before the round ended.

‘Watching the fight, everybody is very much aware I like to brawl.’

Inoue attacked with the jab in the third round, but Cardenas defended well and threatened again with the left, knocking the champion back and following with a solid right.

In the fourth round, both fighters exchanged powerful, punishing punches as Inoue backed the challenger into a corner and unleashed a furious barrage, but Cardenas escaped and responded in a toe-to-toe slugfest as the crowd roared.

Inoue pressed the attack with his left hand in the fifth but took a body punch that backed him off.

An Inoue left to the body hurt Cardenas midway into round six and the champion unleashed a battering series of punches as the American covered up and made it through a round where Inoue landed 33 power punches.

A hard right by Inoue stung, and a solid left to the body doubled Cardenas over in the seventh.