Naoko Fujioka became the first Japanese boxer to be crowned world champion in five different weight classes on Friday, when she claimed the WBO women's light flyweight title.

The 42-year-old Fujioka won a unanimous decision against Costa Rican Yokasta Valle at Tokyo's Korakuen Hall in Tokyo to improve to 17-2 (seven knockouts).

"I thought (Valle) would be a difficult wall (to break down)," said Fujioka. "There was pressure but I feel relieved."

Fujioka claimed the WBC mini fly crown in December 2010 and the WBA super fly title three years later. She won the WBO bantamweight belt in October 2015.

Fujioka added to that haul with the WBA women's flyweight title in March.

"There were times when I lost that I considered retiring, but I am glad that I have kept on going," said Fujioka.