Naoya “The Monster” Inoue has rarely faced adversity during his reign of terror through boxing’s smaller weight classes, but when he finally did against Nonito Donaire, Inoue came through like a champion in a punishing contender for fight of the year.

Inoue, bleeding from a cut over his right eye and nose and hit harder and cleaner than he ever had been, scored an 11th-round knockdown en route to a unanimous decision victory over the probable Hall of Famer on Thursday before a sellout crowd of 20,000 at the Saitama Super Arena in Saitama, Japan.

The judges had it 117-109, 116-111 and 114-113 for Inoue, who unified bantamweight world titles and won the Muhammad Ali Trophy as the winner of the eight-man World Boxing Super Series.

“Donaire was very, very tough for me,” Inoue said through an interpreter. “I see Donaire as a true champion. He’s very strong but I was victorious. I need to get stronger.”

After the 118-pound world title bout came the announcement that has been one of boxing’s worst-kept secrets: Inoue and Hideyuki Ohashi of Ohashi Promotions have signed a multiyear co-promotional deal with Top Rank that will bring Inoue to the United States to fight on ESPN platforms in early 2020.

But that contract was contingent on Inoue, the No. 1 seed in the World Boxing Super Series, prevailing against the old war horse and four-division world titleholder Donaire, who was unseeded.

Inoue (19-0, 16 KOs), 26, of Japan, was ranked fourth in the latest set of ESPN pound-for-pound rankings released Tuesday. The winner of world titles in three divisions (junior flyweight, junior bantamweight and bantamweight), Inoue made his third bantamweight title defense in what was the toughest fight of his career.

He had stormed through the tournament, destroying former world titlist Juan Carlos Payano with a highlight-reel first-round knockout to retain his secondary title in the quarterfinals in October 2018 and then blitzed Emmanuel Rodriguez in two rounds to unify two belts in the semifinals in May. Donaire was as sturdy as they come, but Inoue notched the win to add Donaire’s “super” title to his growing collection.

Donaire was sent to the hospital after the bout for precautionary reasons and released a short time later, his promoter, Richard Schaefer of Ringstar Sports, told ESPN.

Next stop for Inoue is the United States under the new deal with Top Rank. The plan is for him to come to the U.S. for two fights in a row in 2020 before a trip back to Japan for a third fight later next year.

“Naoya Inoue is a generational talent, the sort of fighter who comes around once a decade,” Top Rank chairman Bob Arum said. “He is already a superstar in Japan, and he will be major star stateside in no time. You are looking at an all-time great who is entering the prime of what will be a historic career.”

Inoue, who has won titles at junior flyweight, junior bantamweight and bantamweight, has fought once before in the United States, a sixth-round knockout of Antonio Nieves in a junior bantamweight title defense in Carson, California, on an HBO card in September 2017. He is happy to be on his way back to fight again in the U.S.

“It is a tremendous honor to sign with Top Rank and to showcase my talents on ESPN,” Inoue said. “I look forward to 2020. I’ve fought in America once before, and I look forward to doing so again in the very near future.”

Though the victory over Donaire and the new promotional contract is secured, it was by no means easy getting there.

Inoue, who moved to 14-0 with 12 knockouts in world title bouts, and Donaire traded heavy leather throughout the fight, doing so from the opening round to the final bell.

Inoue knocked Donaire (40-6, 26 KOs) off balance with a left hook in the second round. Later in the second round, Donaire landed a clean left hook that opened a cut over Inoue’s right eye.

It caused him problems for the rest of the fight.

“This is the first cut of my career,” Inoue said. “I had double vision since the second round but I am so happy and proud of myself and I believe I have a bright future.”

In the third round, Inoue began to bleed from his nose.

Inoue had a huge fifth round, rocking Donaire multiple times with right hands. He continued to pound him late in the round and had Donaire on the ropes and unsteady as Inoue did damage until the bell ended the round. By the end of the seventh round, Donaire’s right eye was marked up and swelling.

Donaire had a strong eighth round, landing an assortment of left hands and reopening the cut over Inoue’s eye, which poured blood down his face for most of the rest of the fight. He nearly dropped Inoue in the ninth round when he landed a massive overhand right that rocked him to his boots. Inoue grabbed on to Donaire in order to remain on his feet.

Inoue bounced back to stun Donaire with an overhand right late in the 10th round and then landed follow-up shots.

That set the stage for a scintillating 11th round, a clear candidate for round of the year that featured massive momentum swings. Inoue was on the attack early, and midway through the round he landed a left hand to the body that badly hurt Donaire, who grimaced and took a few steps around the ring before finally going down to a knee.

He barely beat the count from referee Ernest Sharif but then rallied to hurt Inoue before Inoue came back and nearly dropped Donaire again as the crowd went wild.

They continued to slug it out in the 12th round, but it was Inoue getting the slightly better of the action when the bell ended the bout.

Four-division world titleholder Donaire, 36, a Las Vegas-based Philippines native known as the “Filipino Flash,” turned in one of his best performances in years despite the defeat. He looked reborn in the tournament. After a decision loss to Carl Frampton in an interim featherweight title bout in April 2018, Donaire dropped down two weight divisions to join the tournament and return to bantamweight, where he had previously held a title but had not boxed since 2011.

Donaire, the 2012 fighter of the year, who has won titles at flyweight, bantamweight, junior featherweight and featherweight — as well as an interim belt at junior bantamweight — stopped Ryan Burnett in the fourth round due to an injury to win a world title in the quarterfinals in November and then scored a spectacular sixth-round knockout of late substitute Stephon Young, who replaced injured world titlist Zolani Tete, in the semifinals on April 27 to set up the confrontation with Inoue.

Nordine Oubaali retains title vs. Takuma Inoue

In the co-feature, bantamweight world titlist Nordine Oubaali survived a final-round surge from mandatory challenger and interim titlist Takuma Inoue — the younger brother of Naoya Inoue — to retain his belt for the second time. Oubaali, who dropped Inoue in the fourth round, won 120-107, 117-110 and 115-112.

Oubaali, 33, a southpaw from France, rocked Inoue with a straight left hand that sent him into the ropes in the third round. With just under a minute to go in the fourth round, Ouballi (17-0, 12 KOs) nailed him with another left hand on the chin to drop him to his rear end. It was the first time in his career that Inoue (13-1, 3 KO), 23, of Japan, had been knocked down.

Because open scoring was being employed, the scores were announced after the fourth round and Oubaali knew he was ahead on all three. Oubaali maintained his lead and was way ahead when the scores were also announced after the eighth round: 80-71, 79-72 and 77-74 over Inoue, whose right eye was marked up.

Inoue pressed forward trying to change the momentum of the fight in the later rounds and nearly succeeded when he knocked Oubaali into the ropes with a right hand with a little over a minute left in the 12th round. Oubaali was hurt and looking to hold on as Inoue continued to go for a knockout. He landed several punches, but the round ended and Oubaali had survived the crisis.