Asa is a supporting character in the prison setting of Riki-Oh: The Story of Ricky, known for a childlike appearance that belies his status as an inmate. He is introduced as the closest person to a fellow prisoner named Narumi, who is one of the prison's influential figures known as the Four Emperors. Asa is described as a huge admirer of Narumi, indicating a deep loyalty and bond between the two characters. Life within the brutal prison system proves to be particularly harsh for Asa. On his very first day of incarceration, he inadvertently witnessed something forbidden, a transgression for which the punishment was the removal of his tongue. This act of violence left him permanently unable to speak.

Despite his diminutive and youthful look, his presence in an adult prison suggests he is likely a little person. His role in the narrative becomes more prominent through his interaction with the protagonist, Riki Oh. Following a significant fight between Riki Oh and Narumi, Asa and Riki Oh grow close. In a gesture of friendship and perhaps as a means for the voiceless Asa to express himself, Riki Oh gave him a flute. This gift is a poignant detail, offering a form of solace and communication in an environment defined by brutality and silence. Asa's personal code of loyalty is ultimately tested when another character, Yomi, orders him to kill Riki Oh. Asa refuses to comply with this command, a decision that proves fatal, as Yomi kills him for his defiance. No notable combat abilities or specialized skills beyond his close relationships are documented for Asa; his significance to the story is rooted in his loyalty, his victimization by the prison system, and his role in highlighting the bonds of friendship and sacrifice within the violent world of the series.