Rizin FF hosted one of the most surprising press conferences in combat sport history in Tokyo this afternoon. The Japanese promotion produced undefeated boxing legend Floyd Mayweather and announced he would be competing against Tenshin Nasukawa at the Saitama Super Arena on New Year’s Eve.

Up to this point Mayweather has competed exclusively in boxing, amassing a 50-0 record. He is a multiple time world champion whose guaranteed fight purse for his most recent fight, against UFC star Conor McGregor, was announced as being $100 million. That bout broke nearly all box office records.

Tenshin has enjoyed success as a kickboxer and mixed martial artist but has never competed in boxing. There seems to be some confusion about the format of the fight, with Rizin head honcho Nobuyuki Sakakibara admitting that they had yet to agree on either a ruleset or a weight class.

Mayweather’s most recent fight was at 154lbs while Tenshin’s last match was at 127.9lbs. It’s worth noting that the boxer has appeared on a WWE event before, and putting on some sort of exhibition or show would be one way for Rizin to get two men with completely different sizes and skillsets inside the ring.

In his most recent fight Tenshin faced the best mixed martial artist on the Rizin roster, Kyoji Horiguchi. They faced off under kickboxing rules in a matchup that really captured the imagination of the Japanese fight fans with the former winning by decision.