(CNN) - There were doubts to the last whether he would show up.
When he did, Floyd Mayweather wasted little time in outclassing his Japanese kickboxing opponent Tenshin Nasukawa for a first round technical knockout in their New Year's Eve exhibition bout.
The 41-year-old US boxing legend knocked Nasukawa to the floor three times before his young opponent's corner threw in the towel.
"Money' Mayweather earned $9 million for just over two minutes action in a scheduled three round contest.
Nasukawa, less than half his age but with a formidable reputation in his branch of the sport, ended the contest in tears.
Mayweather was carrying a substantial 4kg (9lb) weight advantage into the ring, with Nasukawa facing the added drawback of a reported $5 million fine if he aimed a kick during the bout at the Saitama Super Arena in North Tokyo.
With the odds stacked firmly in his favor, Mayweather appeared not to initially being taking the fight seriously, throwing out gentle punches accompanied by a smile.
But his demeanor swiftly changed as he launches a series of heavier punches to the head of the Japanese fighter, sending him to the canvas after barely a minute.
Nasukawa bravely got to his feet only to be floored again for a second standing count after another flurry of punches from Mayweather.
When he went down for a third time his connections rushed in, the fight over after 139 seconds.
Under the terms of the fight only a knockout or technical knockout was considered a victory, with no judges present, and the result will not feature on the official record of either man, allowing both to keep unbeaten records.
Mayweather, 50-0, came out of retirement to take on the challenge which had shades of his previous lucrative comeback, his 2017 bout against UFC lightweight champion Conor McGregor for which he reportedly earned over $300 million.
That fight in Nevada at least lasted 10 rounds before Mayweather won on a technical knockout and rumors persist he is eying another money making bout with UFC's current man of the moment Khabib Nurmagomedov, who beat McGregor on the Irishman's return to UFC action earlier this year.
After his latest win over Nasukawa, Mayweather insisted that he remained retired, saying the fight had been "all about entertainment for the people."
He added: "I'm still retired. I don't look forward to coming back to boxing.
"This won't go on my record. It won't go on Tenshin's record. Tenshin is still undefeated. I'm still undefeated."
Whether the chastened Nasukawa viewed his pummeling as entertainment is another matter.
The 20-year-old former world junior karate champion turned to kickboxing with great success, building a 28-0 record, claiming he had a "punch that boxers do not have."
Japanese promoters RIZIN clearly believed in his potential, persuading Mayweather to take up the challenge although three days after the fight was announced in November the five-time world champion at different weights had a change of heart.
Under pressure from the promoter, Mayweather then changed his mind again, but right up to the time the fighters did their ring walks there were reports that he would fail to show as the main attraction on a star-studded mixed martial arts fight card.
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