Despite his lofty billing and his Filipino rival's low reviews, Naoya Inoue insists Marlon Tapales is someone not to be taken for granted.

Hosting an open workout in Yokohama on Friday, Inoue expressed his readiness for the 26 December four-belt unification at the Ariake Arena.

"I was able to train with different styles of boxers (in sparring) and our training sessions went very well," Inoue, the World Boxing Council and World Boxing Organization super-bantamweight champion, told the Japanese media.

"I improved a lot and worked on counterpunches," he said.

Tapales, holder of the World Boxing Association and International Boxing Federation straps, is a force to be reckoned with and that he will have to be on red alert the entire match.

"I am afraid of the feeling that Tapales will take a shot at me so I will be very careful about that," said Inoue, who climbs the ring armed with a 25-0 record with 22 knockouts.

Recognizing Tapales' underrated skill set, Inoue believes he will "have to be very cautious" in his dealings with the sneaky and crafty lefty.

Tapales, parading a 37-3 win-loss mark with 19 knockouts, is the massive underdog in the scheduled 12-rounder for the undisputed 122-lb championship.

Almost everyone doesn't think Tapales has a chance of upsetting Inoue, who is widely regarded as the best pound-for-pound in the world, if not one of the best.

But his camp swears Tapales is going to shock the world by becoming the first Filipino undisputed champion.