Naoya Inoue and Paul Butler have agreed to terms on an undisputed bantamweight championship fight Dec. 13 in Japan, sources told ESPN.
Inoue, a star boxer in Japan who is ESPN's No. 2 pound-for-pound boxer, will attempt to unify all four belts for the first time in his career (he holds the WBA, WBC and IBF titles.) The winner of the matchup -- Inoue will be heavily favored -- will be the first undisputed champion at 118 pounds in nearly 50 years.
The fight is expected to be streamed on ESPN+, a Tuesday morning broadcast in the United States.
Inoue (23-0, 20 KOs) captured a third bantamweight title with a second-round TKO victory over Nonito Donaire in a June rematch. The first meeting was named ESPN's 2019 Fight of the Year; Inoue overcame a fractured orbital bone and broken nose en route to a decision victory.
The 29-year-old, a three-division champion, appears destined for the Hall of Fame, a unique blend of speed, power-punching and boxing smarts.
Now, "The Monster" will have the opportunity to effectively clean out the division with the matchup against Butler. The 33-year-old Englishman claimed the WBO's interim title in April with a decision victory over Jonas Sultan.
Butler (34-2, 15 KOs) was twice scheduled to face WBO titleholder John Riel Casimero, but the Filipino withdrew from the bout on both occasions. Following the second cancellation, the WBO stripped Casimero of his title and elevated Butler to recognized champion.
Butler has reeled off eight consecutive wins since a 2018 decision loss to Emmanuel Rodriguez in a title fight. Butler's other defeat also came in a title bout, an eight-round TKO vs. Zolani Tete in 2015.
"I haven't watched his bouts in their entirety, but I can see he is a talented and aggressive boxer," Inoue said in June. " ... If I can unify the four bantamweight titles this year, I would like to move up to the super bantamweight division."