Nasukawa, an undefeated kickboxing sensation who had vowed to "take down Mayweather" was left in tears in the ring but was hailed by his opponent, who claimed on Instagram he will earn $9 million for the bout.
Mayweather insists he will remained retired after the bout.
The rules were strictly defined, with kickboxer Nasukawa reportedly facing a $5 million fine if he directed an iconic kick at Mayweather.
But no. Floyd was not prepared to mess about on New Year's Eve because he held nothing back when the action finally got underway following some absurdly long entrances and introductions.
The undefeated American outclassed Nasukawa in Saitama, Japan from the off as he followed a body shot early on with two further flush blows to the head, before the Japanese's corner threw in the towel.
Nasukawa was called "perhaps the best combat sports prospect [Japan] has ever seen" in the press release for the fight, CBSSports.com reported.
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It was surreal, to say the least.
Many were quick to poke fun at the farcical exhibition fight in Japan, with one user writing: 'Mayweather is an all-time great but there's thousands of 154lbs boxers who could have done that to Tenshin.
Mayweather, 41, a former five-division world champion, floored Nasukawa three times before the end of the first round.
But Nasukawa never landed a meaningful punch. "I'm still retired - I don't look forward to coming back to boxing but I wanted to do this to entertain the fans in Japan".
Mayweather adversary, the great Manny Pacquiao, appeared to get a dig in by saying he would "continue to only fight experienced opponents who are my size or bigger".
"I want the fans all around the world to support him".