Anthony Olascuaga retained his WBO flyweight world title in controversial fashion, defeating Hiroto Kyoguchi by unanimous decision in a scrappy fight at the Ryogoku Kokugikan Arena in Tokyo.

The scores read 117-111, 118-109, 114-113 in favour of the American. But despite an 11th-round knockdown, it was Kyoguchi (19-3, 12 KOs) who arguably landed the bigger, more meaningful punches throughout the fight.

"I'm sorry I couldn't get a knockout today, this guy is a very tough guy," The Ring's No. 7 flyweight Olascuaga (9-1, 6 KOs) said afterwards.

"I had to box when I needed to box, I thought I fought a smart fight but I wish I could've done more. He was a fun fighter to compete with, he has heart, I have honour and respect towards my opponent."

Perhaps with the knowledge that he was entering the final phase of his career, Kyoguchi took his time getting to the ring. He slow-walked to Andre Bocelli's 'Por Ti Volare'. Taking everything in around him, Kyoguchi saw the night as remake or break.

Olascuaga, however, walked with a different energy. Down the ramp he came to Michael Jackson's 'Beat it' and flanked by his pound-for-pound star stablemate Junto Nakatani, this was to be his star-making night.

The first round was a cagey one, but it was champion Olascuaga who landed first; a left hook which saw Kygouchi take a step back. The veteran came back with an attack of his own a moment later, landing to the body before Olascuaga dug in a beautiful counter-right uppercut.

It was Osaka's Kyoguchi who landed the first meaningful punch of the second Round, a beautiful right over the top. Olascuaga managed to use his longer reach to negate much of his opponent's work for the rest of the round, but Kyoguchi would also come back to land several big body shots.

Both men displayed some high-paced, venomous inside fighting to end an all-action second stanza. Already a breathless start from both.

Los Angeles' Olascuaga, who donned pink hair, stepped on the front foot from the off in the third. Both men would trade power jobs from mid-range before Olascuaga welcomed Kyoguchi to meet him in the neutral corner in an attempt to lure his man into something big.

Looking to become a three-weight champ, Kyoguchi looked the happier of both men heading to his corner after the third. And it was champion Olascuaga who had yet to impose his will on his experienced foe.

Kyoguchi began the fourth by Landing two solid jabs, but Olascuaga displayed his best work of the fight but landing a beautifully-timed counter uppercut. Kyoguchi wouldn't be deterred, as back he came with a big right hand and a ripping left to the body.

By the fifth it was clear for all to see that Kyoguchi, whose resume speaks for itself, had the ring IQ to win rounds over Olascuaga. But time would tell on whether Princesa's physical advantages would begin to show.

But it was the smaller man in Kyoguchi who put Olascuaga on the back foot, marching forward, only just missing with a huge overhand right against the ropes. The right landed clean a few moments later, though, and into the bank went another round the way of the home fighter.

"Put him on the ropes," said Olascuaga's trainer Rudy Hernandez to his fighter before the sixth. But that proved more difficult to put into practice as Kyoguchi once again landed the heavier shots in the centre of the ring, one of them a massive right hand. Olascuaga again attempted to get something back for himself, but he swung and missed with a wild left hand.

Olascuaga did land something of note at the end of the sixth, though. A big right hand as both men went to throw at the same time.

The American had some more success in the seventh, finding his range a little easier than he had in the first several rounds. Kyoguchi would still dish out his own punishment in numerous digs to the body, though, and Olascuaga had yet to land anything which commanded the respect of the man standing opposite him.

Back on the offensive went Kyoguchi in the next round; this time a leaping left hand which landed for the home fighter, sending yet another message to the judges that he was the man to pay attention to in there. Olascuaga could only hop around from the outside in an effort to land jabs and potshots.

In the ninth, Olascuaga came close to landing a huge left hook, but it wouldn't put Kyoguchi off. The former unified junior-flyweight champ came right back to push his opponent against the ropes, landing several clubbing blows to the body in the process.

When Olascuaga got himself off the ropes to land something of note back, he was met with a perfect right hand which landed square on the button.

Another beautiful right hand followed for Kyoguchi in the tenth. Back to the outside Olascuaga went, a far cry from what his game plan would and should have been coming into the fight. More swings and misses with both the left and the right, it had become more 'hope to hit' rather than 'hit and hope' for Olascuaga.

Wholesale tactical adjustments were needed from Hernandez in the corner heading into the championship rounds, but whether his fighter would be able to implement them with just six minutes left was another question.

But in the 11th, a breakthrough came for Olascuaga. A flash knockdown, caused by a counter left-hook on the inside. It didn't fluster Kyoguchi, though. He acknowledged the referee's count with a nod of the head and got back on the front foot as if nothing happened. Nonetheless, it was a 10-8 round for the visitor.

The final round saw an ultra-aggressive Kyoguchi come out to try and finish strongly. Olascuaga landed a strong right hand in the middle of an exchange, however, and it was the American who landed the more meaningful punches throughout the final stanza, leaving his opponent off-balance on a number of occasions.

The judges had seen enough throughout the fight to hand Olascuaga the victory with two wide scores of 118-109 and 117-111, while the last card of 114-113 came down to the 11th-round knockdown. A gutting defeat for Kyoguchi, who seemed to accept the loss with graciousness in the ring, shaking his opponent's hand before exiting the ring for, perhaps, the final time.