(CNN) - It's back on. Or so it would seem.
Boxing legend Floyd Mayweather is expected to once again come out of retirement -- this time for a one-off, three-round exhibition match on New Year's Eve against a kickboxer less than half his age.
The bout, the main event on a 14-fight card to be held in Saitama, north of Tokyo, has been the subject of will-he, won't-he speculation, with Mayweather distancing himself from the promotion in November -- saying he had been misled about the conditions.
His change of heart was reportedly reversed when Nobuyuki Sakakibara, head of RIZIN -- the organization hosting the fight -- flew to Mayweather's Las Vegas home for 11th-hour talks, agreeing to rules that would allow the boxer's legacy to remain unsullied.
With everything seemingly settled, the 50-0 legend -- who's been assured that, as there are no official judges and no winner recorded unless there's a knockout, his unbeaten record will remain untouched -- has been coaxed back to Japan.
Posting to his official Instagram account from Tokyo on Monday, Mayweather said he would take home $9 million if he fought.
"What if I told you I was making $9,000,000 for 9 minutes of sparring in Tokyo Japan would you do the same if you were me? I like to call it a 9 minute walk thru," he said.
But even as the clock ticks down towards fight time, doubts remain over whether he'll actually show up.
Mayweather did appear at a Tokyo press conference ahead of the event, as well as a promotional event with his opponent, the highly rated 20-year-old kickboxer Tenshin Nasukawa -- also known as "Ninja Boy."
Even Nasukawa, fresh from training in Las Vegas, has hedged, speaking hours before his opponent in Tokyo.
"I believe the fight will happen," he told Japanese media, referring to the doubts over his opponent's promise to show. "And I'll just perform to my 100 percent. I've been one that's essentially accepted challenges, but this time I'm a challenger. And I have no problem mentally."
Tale of the tape
Assuming the fight goes ahead, the edge is definitely with veteran Mayweather. Standard boxing rules prohibit any kicks -- Nasukawa reportedly faces a $5 million fine should he lash out with his legs -- and Mayweather holds a significant weight advantage.
That said, Nasukawa has the speed and intensity to cause Mayweather problems.
The idea of a cross-discipline fight is not new -- Muhammad Ali once fought Japanese wrestler Antonio Inoki, and Mayweather himself boxed the UFC's Conor McGregor in his last pro fight -- but interest, especially in Japan, has been high since Nasukawa was assigned to the fight.
The youngster, who has a 28-0 record, said when the bout was announced that he relished the chance to meet Mayweather in the ring.
"It's the biggest moment in my life and I want to be the man who changes history. I'll do that with these fists, with one punch -- just watch," Nasukawa boasted.
So assuming he doesn't perform a last-minute about-face, what changed the former five-division world boxing champion's mind and coaxed him out of retirement?
While he's been a consummate professional in an enduring career that's seen him garner 28 KOs, the chance for one more payday presumably ranks high for a man whose nickname is "Money."
While the purse hasn't been officially disclosed, Sakakibara said it would be the largest for an exhibition fight. It's thought to be as much as $18 million, which isn't out of the realms of possibility following Mayweather's social media post stating he would get half that much for the fight.
Mayweather's assumed participation has been a huge driver for RIZIN, which has held 13 major events since its founding and is considered the largest MMA promoter in Japan.
In November, Mayweather told CNN "Talk Asia's" Anna Coren that it had "always been" one of his goals "to go outside the US and compete as a professional in what I love to do."
Not short on confidence
The legend's confidence remains as untouchable as in his heyday. At the pre-fight press conference in Tokyo, Mayweather said the bout would be "just another day."
"I don't have to work hard in the gym for three rounds," he said. "I can basically do three rounds in my sleep, so I don't worry about that."
Mayweather is also confident his record of staying on his feet won't be disturbed. "Throughout my career in boxing, as far as amateur, as far as professional, I never touched the canvas once," he said.
"Me getting knocked out or me getting knocked down ... I don't worry about it at all. If that does happen, I mean that's entertainment. That's all we need to see."
New Year's TV events are a huge part of the Japanese cultural landscape, and most Japanese broadcasters run special programming.
Combat sports have long been a key element of the evening's TV entertainment and consistently receive high ratings.
The official stream of the matchup, on FITE.TV, won't show it in numerous countries, including the US, Mexico, Canada and Japan. It will be broadcast on network TV within Japan.
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