The bout was scheduled to be three rounds but was called after two when Mayweather sent Asakura Asakura to the canvas with a series of heavy right hands at the Saitama Super Arena.
However, the 45-year-old former world champion did not have things all his way. Asakura came out fighting in the first and took the American completely by surprise.
Despite Mayweather trying to keep his distance and find his feet in the first, his agile Japanese opponent was able to throw and land a few stinging blows, much to the delight of the home crowd.
Mayweather was also able to land a couple of punches, though, and came out much more aggressively in the second. This left his defences open and Asakura landed an early right hand to snap his head back.
The American brushed the blow off with a cheeky smile before getting to work. Late in the round, he landed a hard right hand to rock Asakura before throwing a big overhand right that sent Asakura to the deck and ended the fight.
The Japanese fighter did his best to get to his feet and convince the referee that the fight could continue but the official was having none of it and called the technical knockout in Mayweather's favour.
"I'm happy we were able to give the fans excitement," said Mayweather. "Thanks for having me. I'll be back."
Despite his age, this is Mayweather's second fight of 2022 after he destroyed former sparring partner Don Moore in another exhibition fight in Dubai in May.