Having just turned 32 a few days before, boxer Shinsuke Yamanaka said with a bitter smile that having a birthday for an athlete at his age wasn’t necessarily a pleasant thing.

But he added that he felt no decline whatsoever, but rather has room to improve to become a better fighter.

The WBC bantamweight champion, who’s taking on Suriyan Sor Rungvisai of Thailand at Yoyogi National Gymnasium Annex next Wednesday, said that he’d added variations to his boxing techniques and that’d give him a stronger mental edge during a fight.

His ultimate blow, however, is still his potent straight left, which has been described as “God’s left” and given him international recognition in boxing circles, and the fans expect a knockout victory as Yamanaka has always done in the past.

Yamanaka, who’s posted 21 wins (16 KOs) against zero losses, has defended his title six times, and he’s done it with KO wins in the last five. If he sends Suriyan, a former WBC super flyweight champion with a 37-5-1 career record, onto the canvas, he will equal former WBA light flyweight great Yoko Gushiken’s Japanese record for consecutive KO wins in world title matches.

“I’m not aware of the consecutive KO-win record,” Yamanaka said at a public workout for the media at Tokyo’s Teiken Gym on Tuesday. “But I am aware of winning (in the Suriyan bout) in a KO.”

Meanwhile, you might wonder why his opponents still take Yamanaka’s left, though it’s clearly his best weapon. But Yamanaka claimed that he hasn’t stayed at the same level, saying, “I’ve improved every fight (with my left), especially my balance has gotten better with it.”

But as much as he’s put an enormous amount of effort to polish his lethal blow, perhaps it’s a God-given ability.

Tsuyoshi Hamada, a former WBC super lightweight champion and a representative of Teiken Promotions, said that he didn’t remember any other Japanese champions who have had as much of a definitive punch as Yamanaka’s left.

“(Yamanaka) had it when he joined (Teiken), though I don’t believe he’d recognize it himself,” Hamada said. “But he got to know it before he won the Japan title (in 2010).”

Hamada added that Yamanaka, a native of Shiga Prefecture, became a world champion-caliber fighter when he was still a four-round fighter.

Shin Yamato, Yamanaka’s trainer, said that the boxer had recently bought him new custom-made punch mitts that are harder than usual mitts, but Yamanaka’s left stings one particular spot on the mitts and damages his palms.

“That’s something only Yamanaka can do,” Yamato said.