In one of the most jaw-dropping nights in boxing history, Naoya Inoue, the undefeated Japanese pound-for-pound king, was knocked out by John Riel Casimero in the 10th round of a brutal war that shook the boxing world. The clash, which took place at a sold-out Saitama Super Arena in Japan, was anticipated to be a routine defense for Inoue, but instead, it turned into a historic upset.

The brutal KO loss not only cost Inoue his perfect record and unified bantamweight titles, but also triggered a financial avalanche, with sponsors reportedly losing over $45.1 million in post-fight fallout.

The Build-Up: Inoue the Invincible vs Casimero the Underdog

Heading into the bout, Naoya Inoue (26-0, 23 KOs) was widely considered untouchable. Nicknamed “The Monster,” he had steamrolled through multiple weight divisions, defeating elite names such as Nonito Donaire, Paul Butler, and Stephen Fulton. His lethal blend of speed, precision, and power made him one of boxing’s most feared champions.

John Riel Casimero (33-4, 22 KOs), on the other hand, was seen by many as a chaotic wild card. The Filipino slugger, known for his erratic fighting style and controversial behavior outside the ring, was a former three-division world champion looking to reclaim lost glory.

Critics largely dismissed Casimero’s chances, especially given his long layoff, but those familiar with his explosive knockout power knew he was capable of creating chaos.

The Opening Rounds: Tactical Precision Meets Aggressive Chaos

The first few rounds showcased Inoue’s trademark technical brilliance. He dominated the opening rounds with crisp jabs, lightning-fast combinations, and excellent footwork, frustrating Casimero and racking up points.

Casimero, however, didn’t panic. He continued stalking Inoue, waiting patiently for a mistake, bobbing and weaving with unorthodox movement and absorbing shots while looking for an opening to unleash his power.

By round four, Casimero’s pressure began to show signs of wear on Inoue. Though still composed, the Japanese star was forced into more exchanges, slowly being pulled into Casimero’s chaotic rhythm.

Turning the Tide: Casimero Finds His Moment

The seventh round became the turning point. Casimero landed a thunderous right hook to Inoue’s jaw, rocking the champion for the first time in years. The crowd fell silent as Inoue stumbled backward, barely holding on. Though he survived the round, his aura of invincibility had cracked.

From that moment, Casimero smelled blood. He turned up the pressure, cutting off the ring and turning the fight into a slugfest—exactly the type of bout Inoue was trying to avoid.

The ninth round saw the two men exchange heavy bombs. Inoue landed a clean left hook that snapped Casimero’s head back, but the Filipino responded with a ferocious body attack that clearly hurt Inoue. The momentum was fully in Casimero’s favor.

Round 10: The Monster Falls

As the tenth round began, Inoue was visibly tired. Casimero, bouncing on his toes, looked like he was just getting started. Barely 30 seconds into the round, he unleashed a vicious three-punch combo—left to the body, uppercut to the chin, and a looping right hand that crashed into Inoue’s temple.

The impact was devastating. Inoue crumbled to the canvas, his body limp as the referee immediately waved it off. The Saitama crowd was in shock. The Monster had fallen.

The Aftermath: $45.1 Million in Sponsorship Damage

The consequences of Inoue’s defeat were immediate and severe. According to reports from Japanese media, sponsorship and endorsement contracts valued at $45.1 million were put on hold or pulled entirely following the knockout.

Inoue, long seen as a national hero and global ambassador of Japanese excellence, had endorsements with major brands including Asics, Sony, and beverage giant Suntory. Several of these companies removed promotional material within hours of the loss, pending a reassessment of their campaigns.

Marketing analysts noted that while Inoue remains a massive star, his marketability took a major hit, especially in Japan where perfection and honor are culturally revered.

Casimero’s Redemption Story: From Chaos to Crown

For John Riel Casimero, the victory was more than just a title win—it was a redemption arc years in the making.

Following years of inconsistent performances, canceled fights, weight issues, and disputes with promoters, Casimero was dismissed as a has-been. But now, at 35, he has pulled off one of the greatest upsets in modern boxing.

Speaking in the post-fight press conference, Casimero said:

“They said I was done. They laughed when I said I’d knock out Inoue. Now who’s laughing? I told the world, don’t underestimate Filipino power.”

Fans React: A Night No One Expected

Social media exploded within minutes of the knockout.

#InoueVsCasimero trended worldwide on X (formerly Twitter), with thousands of reactions pouring in:

“The Monster just got slain. Wow.”

“Casimero with the KO of the year. No one saw that coming.”

“Naoya Inoue is still a legend, but this proves anyone can fall.”

Even legends of the sport weighed in:

Manny Pacquiao tweeted, “Congratulations, John Riel! You made the Philippines proud again. A true warrior!”

What’s Next for Inoue?

Despite the devastating loss, Inoue remains one of the sport’s top talents. A comeback is expected, and many believe this defeat could serve as a necessary reset.

Promoter Bob Arum was quick to defend his fighter:

“This is boxing. Everyone falls. What matters is how you rise. Inoue will be back, and stronger than ever.”

There is talk of a potential rematch, but some insiders suggest Inoue may move up in weight to rebuild and chase legacy fights in a new division.

Casimero’s Options: Champion Once More

As for Casimero, the possibilities are suddenly endless. He now holds the WBA, WBC, IBF, and WBO titles—an unprecedented feat considering his fall from grace just two years ago.

Potential blockbuster fights await, including:

A rematch with Inoue

A showdown with Nonito Donaire

Or even a unification bout with rising star Ra’eese Aleem

Casimero, known for his brash attitude, made it clear he’s not planning on being a short-term champ:

“I’m not done. This is just the beginning of the Casimero era. Anybody who wants the smoke, come get it.”

Conclusion: A Legacy Shattered and a Legend Reborn

Boxing fans will remember the night Naoya Inoue fell not just for the shocking result, but for the pure drama and emotion that came with it. It was a reminder that in the fight game, nothing is guaranteed.

John Riel Casimero, once the sport’s forgotten man, is now its most talked-about champion. And Naoya Inoue, despite the loss, remains a beloved figure who can—like many legends before him—rise from the canvas and reclaim greatness.

As always, boxing continues to be the sport where legends are born, broken, and reborn. And UFC 319 might be up next, but for now, Casimero’s thunderous right hand owns the headlines.