Tenshin Nasukawa's corner threw in the towel late in the first round during the kickboxer's exhibition boxing match against Floyd Mayweather in Tokyo.
Mayweather knocked the 20-year-old down three times in just over two minutes of the fight which was taking place on the Rizin 14 card.
Mayweather said before the event that he was set to make $9 million for a bout which was scheduled to take place over three, three minute rounds.
Nasukawa, who is undefeated as a kickboxer, is a huge star in Japan.
The rules of the fight stated that it will not go on the official record of either competitor.