Ao turned professional in September 2003 at the Korakuen Hall, Tokyo. In his debut Ao defeated fellow Japanese boxer Hiroshi Kashihara with a second round knockout.
Ao is managed by the Teiken Boxing Gym in Tokyo, and trains under Sendai Tanaka's guidance. He has often attended Marco Antonio Barrera's training camp since 2003,[1] because he was appreciated for his speed and heavy fists,[2] and served as Barrera's chief sparring partner in August 2007.[3]
After thirteen unbeaten fights, Ao beat Koji Umetsu for the Japanese featherweight title in March 2007.
Ao lost via split decision to champion Óscar Larios on 16 October 2008. Despite flooring Larios in the 4th round, Ao managed to lose a decision in the close and contested bout.
Fortunate for him, Ao got another chance at Larios' title on 12 March 2009. There, he applied more offensive tactics which resulted Larios dropping in the 12th round. Ao won the match by unanimous decision.[4] On his first defense of the title held on July 14 that same year, Ao lost to Elio Rojas by unanimous decision.
^WORLD BOXING editorial department (October 3, 2003). 矢代、粟生の2ホープがバレラのキャンプに参加 (in Japanese). MACC Publications Inc. Retrieved February 23, 2011. (the fourth article from the bottom)