Falco (Fou), a B't forged by the Machine Empire as the ultimate weapon for Karen, the West’s Spirit General, embodies the mythical kirin—a winged harbinger of salvation in chaos. His initial reliance on Karen’s blood leaves him inert following her rebellion, abandoned in a scrapyard until revived by Teppei Takamiya, whose blood carries traces of Karen’s essence from her time on Kamui Island. Though skeptical of Teppei’s untested resolve, Falco gradually bonds with the youth through relentless combat, their synergy unlocking his signature abilities: lightning-fast agility, the destabilizing "Sonic Attack," the energy-amplifying "Prism of Aura" fueled by their bond, and the adaptive "Guard System" shielding them from environmental threats.

Shattered in clashes across the Empire’s dominion, Falco is reforged as Neo X by Hokuto using the Break Heart upgrade, augmenting his power and resilience. His journey traces an arc from abandoned war-machine to linchpin of rebellion, countering foes like Demon General Quatro and the Empire’s apex weapon, Rafaello. Rooted in kirin symbolism and mechanical precision, Falco’s evolution mirrors the series’ interrogation of technology and humanity, his loyalty to Teppei underscoring a narrative of redemption through unity against tyranny.