Ryosuke Iwasa claimed the IBF super bantamweight interim title on Saturday after beating Filipino Marlon Tapales by technical knockout.
The 29-year-old southpaw downed Tapales in the 11th round before the referee stopped the match at Barclays Center in New York.
"I'm full of emotion. I had difficulty finding rhythm when I couldn't land my punches, but I was confident because of all of the training I've done," Iwasa said.
"I'm glad I was able to move forward and catch (Tapales) unguarded at the end."
Iwasa improved to 27-3 with 17 wins by knockout, while Tapales fell to 33-3 with 16 KOs.
Iwasa, who made his pro debut in 2008, claimed the IBF super bantamweight title in 2017 but lost to Irish-born TJ Doheny by unanimous decision in August last year.
Doheny was later defeated by Daniel Roman of the United States. The interim title bout was held because Roman was unable to fight due to injury.