Akio was formerly Takumi and Sadao's boss.
Akio made mention before the fight against Yuka, that Takumi and Sadao's boss. Isao made mention of the two possibly being ordered by Akio, though he denied it saying that 'Number One had been on edge lately' because of Kei's interference. When there was no choice but to fight, he showed that he had a more sadistic side to him, enjoying and relishing in the fact. In order to make Yuka bend to his will, he used a technique that tied his and Mai's fate together. He then proceeded to beat the living crap out of Yuka, while demanding that she beg for Mai's life. Mai stepped in, however, and used his own technique against him. She forced him to cut the string and cancel out the technique, after which, Mai shot him point-blank, killing him.