Naoya Inoue became a four-division champion in the early hours of Tuesday morning when he knocked out Stephen Fulton to win the WBC and WBO junior featherweight titles in Tokyo, Japan. A vicious right hand in the eighth round wobbled Fulton before a left hook sent him to the canvas. Fulton made the ten-count, but still remained dazed as Inoue unloaded a barrage of punches before the now former champion dropped to the ground and the referee called an end to the action.

While the win further cemented his place as one of the best lighter weight fighters in the world as well as being among the top ranks of many pound-for-pound lists, it's time Naoya Inoue was considered the very best pound-for-pound boxer in the world — even over the likes of Canelo Alvarez and Terence Crawford.

Inoue's win was made all the more impressive given that Fulton was not only previously undefeated and arguably the best junior featherweight in the world, but that Inoue was the smaller man fighting at 122 pounds for the first time in his career. And yet, he dominated the Philadelphia native over the course of the fight with the finish proving why he is aptly named “The Monster.”

“Everything I was thinking about was to fight (Fulton) this year,” Inoue said after the fight. “However, unfortunately, I got injured, and I had to postpone this fight. I am sorry to my team and Fulton’s team but thank you so much for accepting this fight once again. I am so happy right now.”

The Japanese superstar is now 25-0 and an impressive 20-0 in title fights with 18 of those coming by knockout. Most pound-for-pound lists already have the 30-year-old in the top three at the very least with most having either Terence Crawford or Canelo Alvarez at the very top. However, Inoue's case as the very best is stronger than ever.

For starters, like Crawford and Alvarez, he also unified a division when his 11th-round knockout of Paul Butler back in December saw him hold every title at bantamweight. One more potential win against WBA and IBF junior featherweight champion Marlon Tapales could see him completely unify another division in the space of a year.

Being the pound-for-pound best means dominating in multiple divisions. Crawford is undefeated like Inoue, but he's only a three-division champion. And while Alvarez is also a four-division champion like Inoue, he's suffered two professional defeats, most recently to Dmitry Bivol in their light heavyweight title fight last year in what is the heaviest weight class he's fought in. That's without mentioning the many fights boxing observers felt Alvarez got favorable decisions in and should have lost.

Inoue, meanwhile, not only won titles in his fourth division, but did it in dominant fashion against the very best the division had to offer. Prior to that, his toughest test came against Hall of Famer Nonito Donaire where despite suffering a fractured orbital bone and broken nose, Inoue showed his heart and warrior spirit to come out with the unanimous decision win in their bantamweight title fight back in 2019. Inoue has seemed almost untouchable otherwise — he'd even win his eventual rematch with Donaire in 2022 with a second-round TKO.

Of course, recency bias often swings opinions in combat sports. In the UFC, for example, the title of ‘pound-for-pound best' seems to fluctuate with each victory from Jon Jones or Alexander Volkanovski. A similar phenomenon could occur here as Inoue's win has some unfortunate timing. Should Crawford win his upcoming welterweight title unification clash against Errol Spence Jr. on Saturday, he could potentially be crowned the pound-for-pound best, or further cement his claim to the title.

While it wouldn't be completely undeserved as a win over Spence would still be absolutely massive, recency bias shouldn't take away from what Inoue has and continues to achieve. Inoue has already set his sights on further accomplishments, aiming to become undisputed junior featherweight champion by the end of the year by defeating Tapales.

At this rate, it looks very likely that he'll do just that and while 126 pounds may be a step too high, given his current trajectory, who can doubt Inoue's ability to conquer a fifth division? After all, he revealed pre-fight that he planned on “pushing the boundaries of my build, my limits” — perhaps featherweight could be next on the horizon.

As it stands, Inoue is already and should be widely considered the pound-for-pound best boxer in the world, and adding yet another title from a fifth division to his collection would only further cement his case.