Ashura-oh is the protagonist of the story, born as the last surviving member of the Ashura clan. His birth occurred after the villainous Taishakuten had already killed Ashura-oh's father and seized the throne of Heaven. At the same time, his mother, Shashi, gave birth to Taishakuten's son, Ten-ō. Viewing Ashura-oh as an obstacle who would stand in the way of her ruling Heaven alongside Taishakuten, Shashi attempted to kill her own child. However, Ashura-oh's innate powers protected him, enclosing him in a cocoon where he slept undisturbed for three hundred years.

He was eventually awakened from this cocoon by Yasha-ō. Upon being freed, Ashura-oh first appeared as a baby but grew rapidly to the apparent age of about eight years. Initially, his personality was outgoing and friendly, but he soon became acutely aware of his cruel destiny. This realization came when Taishakuten had almost everyone Ashura-oh had associated with killed. Overwhelmed with guilt for their deaths, Ashura-oh vowed to become strong enough to defeat Taishakuten himself.

There is a profound duality to Ashura-oh's nature. Beyond his innocent exterior lies another side: he is the true Ashura, a merciless god of war whose core desire is the total destruction of Heaven, Earth, and Hell. This destructive aspect was kept in check by several seals, one of which involved the distribution of his true power among the Six Stars. The seal is broken when the Six Stars gather, unleashing his full destructive potential. Ultimately, it is only his deep love for Yasha-ō, his adoptive father, that triumphs over his overwhelming lust for destruction.

A crucial element of Ashura-oh's background is that he was born genderless. This condition was a punishment for his father's sin, specifically to prevent him from continuing the royal line of the Ashura clan. This destiny was something Ashura-oh desperately wished to defy.