Fao holds the position of West Spirit General in the Machine Empire, initially responsible for defending against intruders such as Teppei Takamiya. He embodies pacifism and philosophical depth, often grappling with violence despite his exceptional combat prowess. A prominent scar on his face stems from a defining act of betrayal by his former friend Quattro during their youth, profoundly shaping his worldview and sense of duty.

Fao's loyalty to the Machine Emperor falters following encounters with Teppei and unfolding events within the empire. He questions the emperor's motives and the empire's oppressive nature, ultimately aligning with Teppei and other rebelling Spirit Generals. This path culminates in a pivotal confrontation where Fao directly faces Quattro, resolving their long-standing conflict through decisive battle and achieving personal redemption.

His partnership with his B't, J'Taime, reflects deep mutual respect and seamless combat coordination. During the final battle against the evolved B't Raffaello, Fao and J'Taime join fellow Spirit Generals in a sacrificial act. They contribute their life energy to activate a fragment of the sun, an essential action to destroy Raffaello and avert global catastrophe. This sacrifice marks the culmination of his transformation from loyalist to selfless protector.