Fao holds the position of the West Spiritual General within the Machine Empire, a powerful organization where he is initially entrusted with defending its territory from intruders. A prominent scar on his face is a permanent reminder of a formative act of betrayal by his former friend Quattro during their youth, an event that profoundly shaped his worldview and his sense of duty. This injury, along with his experiences as a child in a place called Sodom, led him to a complex and philosophical perspective on faith and violence, a path that eventually resulted in him becoming a priest. He is characterized by a deep-seated pacifism and a thoughtful nature, often grappling with the morality of his own exceptional combat prowess.

Fao’s primary motivation gradually shifts from loyalty to the empire to a personal quest for truth and redemption. His initial role as an antagonist puts him into conflict with the protagonist Teppei Takamiya. However, for reasons tied to his own moral code, Fao saves Teppei’s life and cares for him at an orphanage, an act that constitutes a direct betrayal of the Machine Empire. This decision sets him on a path as a rebel, where he begins to question the emperor’s motives and the oppressive nature of the empire.

His most significant relationship is with Quattro, the former friend whose betrayal left him scarred. Their long-standing conflict becomes a central point of his personal journey, culminating in a decisive confrontation where Fao achieves redemption by resolving their tragic history. Another crucial relationship is with his Bt, a sentient fighting machine named JTaime. Their partnership is built on deep mutual respect and seamless coordination in battle, reflecting a bond that goes beyond a simple master-servant dynamic. Fao also develops an alliance with Teppei and the other Spiritual Generals who choose to rebel against the Machine Emperor.

Throughout the story, Fao undergoes a profound transformation. He begins as a devoted, if internally conflicted, servant of the empire, resigned to his fate and carrying the weight of his past sins. Through his encounters with Teppei and his decision to follow his own conscience, he transforms into a selfless protector. In a climactic final battle against the evolved and devastating Bt Raffaello, Fao and JTaime join forces with the other Spiritual Generals in a sacrificial act. They willingly contribute their life energy to activate a fragment of the sun, an essential action taken to destroy Raffaello and avert a global catastrophe. This sacrifice marks the culmination of his evolution from a loyal enforcer to a warrior who gives his life for the greater good. Fao’s notable abilities include his skills as a hand-to-hand combatant, honed through his training as a Spiritual General, and his capacity to command and fight in perfect sync with his powerful Bt, JTaime.