The fight will be at the Saitama Super Arena, but what form it will take is not yet clear.
The undefeated 41-year-old, who has won world boxing titles in five different weight categories, has never fought professionally in MMA and it has yet to be decided what format and rules the fight would follow. "But we told the people anything is possible, so now we're here and we want to make sure that we give the people in Tokyo what they want to see: blood, sweat and tears".
Floyd Mayweather Jr. (50-0, BX) has a legitimate case as the best boxer of all time, and he has the record to back it up.
Mayweather, who stopped McGregor in the 10th round previous year after coming out of retirement for a $275 million pay day, had been flirting with the idea of a rematch with the Irishman or facing McGregor's recent MMA conqueror, the fearsome Russian Khabib Nurmagomedov.
"I'm not really anxious about the weight class or rules - it's about me displaying my skills against another skilful fighter".
Instead, Mayweather explained that the decision to fight in Japan was about expanding his global profile.
"I want to continue coming over here and bringing other fighters so my company can continue to grow and RIZIN can continue to grow".
Japan's Nasukawa, 20, competes in the RIZIN Fighting Federation, the company Mayweather has signed with, in both kickboxing and mixed martial arts.
"I'm older now", Mayweather said.
Rizin chairman Nobuyuki Sakakibara, who used to run the now-defunct Pride Fighting Championships promotional company, said they were still working out some of the details. Are you excited to see it? "I'll do that with these fists, with one punch - just watch". "When I was offered this card, I accepted it right away without any delay whatsoever".
'I can wrestle, I can wrestle a little bit. "My opponent looks taller than he actually is, but I think I could hit him". I'll speak with my team and get with Rizin to come up with a great idea. "I love to entertain, I like for people to be entertained and who doesn't want to be entertained".
Ariel Helwani said tonight that the rules and weight still had to be worked out.