Japan's Kosei Tanaka successfully defended his WBO flyweight title for the second time after defeating Puerto Rico's Jonathan Gonzalez by technical knockout in Nagoya on Saturday.

Tanaka downed the Puerto Rican southpaw with punishing body blows in the third and fourth rounds at Takeda Teva Ocean Arena before the referee stopped the match shortly before the bell in the seventh.

"I was thinking that my strategy would be to make it a contest of speed, but I wasn't able to," Tanaka said. "Still, I think I have the ability to win like that."

Tanaka's father, who is also his trainer, said, "I gave him instructions to get it done (before the start of the seventh round). I noticed that if he fights with confidence, he'll get that kind of result."

The 24-year-old undefeated Japanese boxer improved to 14 wins with eight by knockout, while Gonzalez fell to 22-3 with 13 KOs.

Tanaka, a three-division champion with previous world titles at minimumweight and light flyweight, won the WBO flyweight belt off fellow Japanese Sho Kimura last year and beat compatriot Ryoichi Taguchi in his first defense in March.