Three-belt world bantamweight boxing champion Naoya Inoue will fight WBO champion Paul Butler of Britain on Dec. 13 in Tokyo in a bid to unify the four major titles in the division, his Ohashi Gym said Thursday.

WBA, WBC and IBF champion Inoue, 29, nicknamed "Monster" for his domination in the ring, will bring an undefeated record of 23-0 with 20 knockouts into the bout at Ariake Arena against the 33-year-old Butler, who has a 34-2 record with 15 KOs.

Inoue became a three-weight world champion in May 2018 when he knocked out Jamie McDonnell of Britain in the first round.

Inoue became the first Japanese to have won world titles under three different sanctioning bodies with a second-round technical knockout of Nonito Donaire of the Philippines this past June