Quietly-spoken and unerringly polite away from the cage, Aoki's arsenal of locks, chokes and strangles makes him one of the most dangerous submission specialists in the world of mixed martial arts.
With black belts in judo and Brazilian jiu-jitsu, Aoki claimed the DREAM lightweight title in 2009 and was once ranked among the world's top five lightweights.
The 29-year-old will get the chance to burnish his reputation further when he fights champion Kotetsu Boku for One Fighting Championship's lightweight crown on April 5, but for many he remains a divisive figure.
The image of a leering Aoki giving Mizuto Hirota the middle finger shortly after breaking Hirota's arm on New Year's Eve 2009 drew the wrath of the entire MMA world and left a stain on the Japanese fighter's career.
Aoki's mood darkens when the subject is raised. The engaging smile disappears and he hangs his head, searching for the words to describe the night bad blood boiled over. Or perhaps he is just sick of the question.
"It's not a good memory for me," he tells Reuters in an interview on Monday. "I've already apologised for what happened with Hirota. Both of us are tired of being asked about it.
"What happened happened, but it's time people accepted that it's in the past and let me move on."
Since losing to Glibert Melendez in 2010 and to Eddie Alvarez last year, Aoki has slipped down the rankings but remains one of the most respected, and feared, fighters in Asia.
He would readily accept a rematch with Melendez or Alvarez, who he beat in 2008, but says he won't go looking for the fight.
"Of course if there was a chance to fight Melendez or Alvarez again I'd fight them," he added. "But since I lost to them I don't think it's right for me to ask for a rematch. It's not my place to say: 'I lost but I want to fight you again.'"
There are no shortage of fighters eager to get their shot at Aoki in Asia.
After beating brash Frenchman Arnaud Lepont with a slick triangle choke in Singapore last October, Aoki punched Antonio McKee to a stoppage in Tokyo in December and will look to make it three straight wins against Boku in April.
ONEFC official Loren Mack said Aoki was a marquee signing for the promotion.
"Aoki is one of the greatest mixed martial artists competing today," he told Reuters. "Aoki sells out arenas in every fight that he is in, and Aoki vs Boku is considered the biggest fight in Asian MMA history."
While critics say Aoki can be too one dimensional, relying too much on his ground game, Mack said his striking skills were evolving and he was still near the top of the lightweight tree.
"Aoki is already one of the top lightweights in the world. In his last fight, he defeated his opponent by strikes which is a clear indication that his striking is improving with every fight that he is in," he said.
"Boku is going to be his biggest test yet because Boku has one punch knockout power and is one of the most well-rounded mixed martial artists that Aoki has ever faced."
Aoki will be a heavy favourite against Boku but he knows anything can happen in MMA. He will not make the mistake of underestimating him.
"I always feel afraid before a fight. Every time," he added. "And afterwards there's a great sense of relief that washes over me. It's like that all the time. Fear, relief. Fear, relief.
"It's such a scary thing to step into the cage."
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