Floyd Mayweather just can't seem to stay retired.

The boxing legend is set to fight the rising kickboxing star Tenshin Nasukawa on New Year's Eve at the Saitama Super Arena in Saitama, Japan. The 20-year-old is no slouch, with a 27-0 record and 21 knockouts.

Mayweather and Nasukawa announced the bout together during a news conference in Tokyo; however, the specific details of the fight were not discussed. Fans of the two will have to wait and see if the fight will be boxing, or MMA.

"As far as the weight class and the rules we'll talk about that," Mayweather said, according to ESPN. "We'll get that situated within the next couple of weeks. This particular bout is a special bout as far as we're giving the people something they've never seen before. The world has never seen Mayweather compete live in Tokyo. Throughout the years I've seen a lot of fans from Japan come to Las Vegas and come to the U.S. but me and my team said let's do something different. Let's go over to Japan."

For those that were taken aback by the surprise announcement, Rizin promoter Nobuyuki Sakakibara attempted to explain why the Japanese promotional company decided to partner with the 41-year-old superstar.

“I think my shortest answer to that is the fact that now we are aligned to achieve something together and that is hitting a new challenge, taking a step forward to whatever wonderful thing that we can create together,” Sakakibara said, according to MMA Fighting.

Mayweather, never one to shy away from a challenge, posted a photo on Instagram before the announcement. The caption read, "December 31st 2018 #Tokyo."