Ao is the former Blue Dragon, the bearer of the dragon's power before the character known as Shin-ah. He lived in the hidden village that reveres and fears the Blue Dragon lineage, and it fell to him to raise the next Blue Dragon after the child was born and his mother took her own life. Ao's life was marked by the same isolation that defines the role, having been shunned by the rest of the village and forced to live apart. This experience left him a deeply bitter and harsh individual. He took his anger and despair out on the young, nameless boy in his care, raising him with strict, cold severity. He taught the child swordsmanship to fulfill his duty of protecting the village but also instilled in him the fundamental rules of their existence: never take off the mask that hides his eyes, and never speak to or go near any of the other villagers. On the surface, this treatment seems cruel, but it was motivated by a tragic understanding of the future that awaited the new Blue Dragon. Ao was preparing the child for the inevitable life of loneliness and rejection he would face, believing this harshness was the only way to equip him for a world that would never accept him.

As the child grew and his own powers developed, Ao's dragon abilities began to wane. His most notable ability, the enhanced eyesight that defines the Blue Dragon's power, gradually deteriorated until he became completely blind. In a rare moment of tenderness during this time, the young boy found some bells and put them on his mask. The jingling sound allowed Ao, now sightless, to locate the child, and this small act of kindness from his charge touched the embittered former guardian. Despite this brief connection, Ao eventually lost the last of his powers and died, leaving the new Blue Dragon completely alone as he had always known he would. His final words included an apology for leaving the boy by himself. Ao's role in the story is therefore entirely within the backstory of Shin-ah. He serves as a tragic figure who, despite his abusive methods, genuinely cared for the boy he raised, representing the cycle of pain and loneliness that defined the Blue Dragon's legacy. After his death, the new Blue Dragon names his only companion, a pet squirrel, in his memory, signifying the complex and lasting impact Ao had on him.