On Boxing Day appropriately, December 26, live on Sky Sports, 'The Monster' Inoue fights Marlon Tapales at the Ariake Arena in Japan.

Inoue brilliantly won the WBC and WBO super-bantamweight titles in his last fight, his first at 122lbs, when he knocked out excellent American Stephen Fulton.

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With Tapales the holder of the IBF and WBA belts, this clash offers Inoue the chance to become a two-weight undisputed champion.

Winning that would place Inoue in august company. In the four-belt era so far only one man, Terence Crawford, has gone undisputed in two weight classes.

Inoue's track record of achievement is phenomenal. He first won a world title at light-flyweight, in just his sixth pro bout.

He won a championship at super-flyweight before jumping up to bantamweight, where among his impressive victories he smashed Jamie McDonnell in a round and won a thriller against Nonito Donaire, before dismissing ' The Filipino Flash' in just two rounds in a rematch.

He became the undisputed bantamweight champion last December, and if he beats Tapales will go undisputed in his second weight class in just over a year.

What has made such an impression too is the style of his victories.

"A special fighter, he does everything well. Everything. I can't find a fault in him," said Hall of Famer Jane Couch.

Gary Logan, a boxing trainer and pundit, noted: "And what he's really good at, if you do find a weakness, he quickly closes that door. He quickly closes that door and finds an answer to the answer that you think you've found.

"He did it with Fulton in the last fight where he kept touching Fulton with a hard jab to the stomach. Before Fulton realises it, to protect his stomach from that hard jab, he's dropped his left hand and he [Inoue] has brought through that right hand over the top.

"He's always cleverly pressuring you and looking at your mistakes that you're making while he's pressuring you. So in effect, he's quite an aggressive counter-puncher.

"But he can also lead as well because he's got that one-two snap, that rare power, that rare timing. If you had to put him in a box, it's the rare timing that he has that gives you that snap.

"He's knocking out men that look decidedly bigger than him and you could see him going up to featherweight and doing it.

"Tapales is not to be underestimated but how many times have we said that and he's still gone out there and chinned him."

Josh Taylor knows better than almost anyone what it takes to become an undisputed champion. The Scotsman achieved that feat at super-lightweight.

He's also fought on the same card in Glasgow as Inoue. "He's a great fighter and I'm a very big fan of him," Taylor said.

He considers Inoue to be currently one of the best fighters in the world at any weight. "He's got to be either No 1 or 2. There will be only two two-weight undisputed world champions [if Inoue beats Tapales].

"Those two guys have got to take No 1 and No 2. Absolutely. You've definitely got to have an argument whether it's him or Crawford."

Todd duBoef, of Top Rank which promotes Inoue, believes the Japanese star has already established himself as the pound-for-pound best in the sport.

"It's hard not to recognise him as pound-for-pound No 1 just because of his body of work. He's always fighting the best out there, regardless of the weight division and he's one of those just determined athletes," duBoef told Sky Sports.

"I've been in the business since 1993 and when I saw all these guys coming up, you could just see special fighters.

"Whether it was Floyd Mayweather, whether it was Kostya Tszyu, whoever it was and he has that. He has that ability. He has that 'it' factor, where he's got speed, power, IQ and just pure domination.

"I think most people would say the Donaire fight, the first one was a very competitive, wonderful fight. He got tagged early in the fight and fought probably at 60 per cent because he had a broken orbital socket and still handled him, but it was a terrific fight.

"He is a special, special fighter across the board," he added. "His popularity in Japan is just unbelievable. We would love to have him in America but he is doing such wonders for the sport in that country."

Opinion is split between Inoue and Crawford as to who is the pound-for-pound No 1.

"I think pound-for-pound lists are difficult. You're as good as your last fight and it's whose performance was the most outstanding recently. Everyone jumps on that. Crawford was sensational against Spence but in a way in terms of consistency, he [Inoue] is pretty much sensational every single time," said former world title challenger and Sky Sports pundit Matthew Macklin.

"He's certainly in that conversation. I think most people would have him No 1 or No 2. I would say the general consensus is it's between Inoue and Terence Crawford."

Sky Sports commentator Andy Clarke reckons Crawford does have the edge on that front at present. "If Inoue beats Tapales, he'll become undisputed in his second weight division but I would still put him behind Terence Crawford, I think because Crawford's achievement of unifying at welterweight, I would put above Inoue's at super-bantamweight," Clarke said.

"Because he beat [Errol] Spence and that was a massive fight. I'd put their achievement at bantamweight and super-lightweight relatively even. So I would give Crawford the edge over 'The Monster'.

"I would still put Crawford ahead of Inoue [now] because his win against Spence to unify at welterweight and the manner of it, given the opposition, will top Inoue unifying against Tapales."

But that is a staggeringly high bar and Inoue could certainly outshine Crawford in future, especially if he moves up to yet another weight class.

Inoue, Todd duBoef believes, can and will do just that. "Could he run through the 126lb division? I wouldn't put anything past him. Probably," duBoef said.

"Depending on the '30lber I think you could possibly put him in a '30lbs match but I think he's going to really cap out at 126lbs.

"For size purposes, I'm not sure we see Inoue above 126lbs."

Winning titles there, in a strong featherweight division, would put Inoue at the very summit of the sport, although Oleksandr Usyk could join him and Crawford as a two-weight undisputed champion if he were to beat Tyson Fury in February.

Clarke noted: "It's always possible of course if Inoue moves up to featherweight, I think we all expect that he will, then maybe he could eclipse [Crawford] by winning a world title in that weight division. There's Usyk to consider as well. If he beats Fury then he's right up there."

Matt Christie, editor of Boxing News, said: "It's a difficult business predicting where a fighter will be ranked if they win in a fight that is yet to happen. I think in the case of Naoya Inoue, who we all know is a wonderful, talented and exciting fighter, even if he looks like I think he's going to look on Boxing Day and wins in good style, at Boxing News we still will have Terence Crawford as the sport's leading fighter.

"I think if you look at what he did in 2023, albeit in just one performance, in the victory over Errol Spence who for a long time was regarded as Crawford's closest rival, and many before that fight thought that Spence would win, the manner in which Crawford took him apart I think sets a very high benchmark in the sport that even Inoue at the moment can't quite match.

"But what we're set for in the sport of boxing, with these two leading the way and potentially Oleksandr Usyk in February to join them is a sport that's very, very healthy at the top."

Watch Inoue vs Tapales live on Sky Sports on the morning of December 26, the undercard from 8am, main event after 10am