Seiya Tsutsumi's relentless pressure earned him a unanimous points decision victory over Takuma Inoue for the WBA world bantamweight title in Tokyo on Sunday.
The 28-year-old Inoue (20-2, 5 KOs), whose elder brother Naoya is the undisputed world junior featherweight champion, lost the title in a third defense after Tsutsumi was awarded scores of 114-113, 115-112 and 117-110 at the Ariake Arena.
Tsutsumi (12-0-2, 8 KOs), 28, produced a tireless display in his first world title win and had to contend with a nasty cut above his left eye for the final two rounds.
He could next fight WBC champion Junto Nakatani (28-0, 21 KOs), also from Japan. Nakatani first defends his belt against Petch Sor Chitpattana on Monday in the second leg of two back-to-back shows in Japan.
Inoue, from Yokohama, made a good start, but Tsutsumi outworked him from Round 3 to the midpoint of the fight.
Inoue landed a good right hook in the seventh, but Tsutsumi's volume of hooks kept him in control for most of the rounds. Tsutsumi's pressure just didn't allow Inoue to settle and establish his jab, and Inoue was restricted to single shot success.
Inoue was upset to be given a count in Round 10 after he was caught by a left that sent him staggering into the ropes. Late in the same round, Tsutsumi suffered a cut by his left eye.
Inoue sensed he needed a big finish and, in the last round, both stood toe-to-toe and traded blows in a thrilling finish to an intense encounter.
Also on the bill, Kenshiro Teraji stopped Cristofer Rosales in Round 11 for the vacant WBC world flyweight title to become a two-weight world champion.
Blood flowed from Rosales' nose from early in the fight, and the injury prompted the bout to be stopped in the 11th round following advice from the ringside doctor.
Teraji (24-1, 15 KOs), 32, from Kyoto, had two reigns as WBC junior flyweight champion from 2017, punctuated by one defeat in 2021, before stepping up a division to face Nicaraguan Rosales (37-6, 22 KOs), 30, a former champion.
Shokichi Iwata (14-1, 11 KOs), 28, from Tokyo, flattened Spain's Jairo Noriega (14-1, 3 KOs), 31, with a left hook in Round 3 to win the vacant WBO world junior flyweight title.