The fight, which will be contested under "special rules", is slated on New Year's Eve at the Saitama Super Arena.
A world champion at five different weights in boxing, Mayweather has never fought in mixed martial arts and it has yet to be decided what rules and format the fight, which will take place in Saitama, will follow.
Mayweather last fought in August 2017 when he won a 10th round TKO against Conor McGregor, who crossed over to boxing for the fight that became the second biggest pay-per-view of all time.
Since achieving his flawless record of 50 wins when he beat Conor McGregor back in August 2017 the former five-weight world champion has talked about fights with the UFC champ Khabib Nurmagomedov and boxer Manny Pacquiao, but not so much with the kickboxer.
"As far as the weight class and the rules, we will talk about that and will get that situated within the next couple of weeks", he said.
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Floyd Mayweather won all 50 of his boxing fights.
Rizin FF announced Sunday night that Floyd Mayweather will return to the ring on New Year's Eve to fight undefeated kickboxing sensation Tenshin Nasukawa. While the odds of a Mayweather-McGregor bout in the Octagon still feels like a long shot, Floyd "Money" Mayweather has never been known to turn down a fight if the price is right. Are you excited to see it? I'm a little surprised myself. "My punch can change history and I will show that to you".
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. "I can do anything if I set my mind to it".
"I think my role as a fighter is to make sure that fighting here in Japan gathers a lot of excitement", the Tokyo native said through a translator.
"I want to continue to build my relationship with Money Team Tokyo", he added, promoting the cross-code bout as an expansion of his businesses into Japan.
The rules of the fight are still being worked on, according to ESPN's Ariel Helwani.