"As far as the weight class and the rules, we'll talk about that", said Mayweather, who was dressed in a red, white and blue sweat suit and flanked by One Entertainment's Brent Johnson, who represented him in making the deal with Rizin.
The undefeated 41-year-old, who last year said his boxing career was over after beating Irish MMA fighter Conor McGregor, has told Reuters he could handle himself in whatever format was agreed for the fight on New Year's Eve in Saitama.
'We will just see.
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.
Since achieving his ideal 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.
Although the ruleset and weight class for the shock bout haven't been announced, Mayweather has insisted they will "get situated" in the coming weeks.
When asked when Rizin FF will finalize the details of the Mayweather vs. Nasukawa fight, Sakakibara could not give an immediate answer. "It's great. I want to say congratulations to Tenshin and Rizin and just everybody for backing this event".
It is unclear what rules be in place when Mayweather and the undefeated Nasukawa enter the ring, but Mayweather has indicated that he is in the midst of determining this with the promotion company, Rizin FF. Rizin's president Nobuyuki Sakakibara announced that the fight is likely to occur using "special rules".
"When I was offered this, I accepted right away without any delay whatsoever", he said through a translator. Honestly speaking, I'm a little surprised myself.
"It's the biggest moment in my life and I want to be the man who changes history". "Boxing rules I wouldn't mind". I think when it comes to experience, I have more experience on my side but when it comes to youth, youth is on his side.
"I am pretty sure that when I speak with the guys from my team we are going to get on the same page so we can go out there and do what we have to do", he added.
'I wanted to do something different.
ESPN reporter Ariel Helwani said it was unlikely to be an MMP bout.