The undisputed title fights just keep on coming.

On Wednesday, ESPN’s Mike Coppinger reported that Ring, IBF, WBA and WBC bantamweight champion Naoya Inoue will face WBO counterpart Paul Butler in Japan on December 13.

The unbeaten Inoue (23-0, 20 KOs) has already captured titles in three weight classes and he could move on to a fourth. The Japanese star was rumored to be heading to junior featherweight, with many fans savoring a potential clash with unified titleholder Stephen Fulton.

However, the lure of making history has kept “The Monster” at 118 pounds for now. Should Inoue prevail over Butler, he will not only match the achievement of Japanese hero Fighting Harada – who was undisputed bantamweight champ in the sixties – he’ll also be the first fighter to hold all the belts in this division since 1973 (Enrique Pinder).

Butler (34-2, 15 KOs) is a two-time bantamweight titleholder. Talented, quick and crafty, the Cheshire, England, native is coming off an impressive 12-round unanimous decision win over Jonas Sultan. That victory saw the 33-year-old claim the WBO interim title and he was upgraded to full champion shortly thereafter when John Riel Casimero was stripped.

“I’m really happy for Paul,” Butler’s trainer Joe Gallagher told The Ring. “People wrote him off, but he became a world champion and now he’s a two-time world champion. This is a really good opportunity to fight for all the marbles. Inoue is undoubtedly one of the best pound for pound fighters in the world at the moment. It’s a huge challenge but it’s one we’ll be fully prepared for.

“Inoue always comes prepared and he always knows what to do with the opponent. He’ll have watched a few of Butler’s fights and he’ll come up with a game plan on how to beat Paul. We’ll have to look at things a different way and bring something to the table that he hasn’t seen before.”

This will be Butler’s first time fighting outside of the U.K. and he will be a significant underdog.

Inoue-Butler will be broadcast live on ESPN+ in the U.S. and Amazon Prime Video in Japan.