Snow Langley bears long snow-white hair usually secured in a ponytail and piercing blue eyes. He wears a black outfit, a necklace with a tiny sword pendant, a white belt, and dark brown thigh-high boots.

Born with clairvoyance allowing him to see demons, Snow grew up in an orphanage with his younger sister, Wisteria Langley. They were later separated under the false pretense of Snow becoming a town servant; in reality, he was recruited into the demon-slaying Knights of the Sword Cross. During his service with the Knights, he worked alongside fellow member Takenami.

Snow's driving motivation is his profound love for Wisteria, fueling his relentless search for her. Discovering her contract with the demon Marbas, he initially assumes Marbas manipulates her and reacts with hostility. He maintains this antagonistic stance for a significant time, even vowing to kill Marbas should Wisteria come to harm.

Experiences in the Afghan War alongside comrades Luther Roosevelt and John Watson shape his background. A later reunion reveals Luther as a contractor intending war against the Knights of the Sword Cross, profoundly shocking Snow.

Snow actively participates in Knights' operations across various story arcs, including the Blackbell Family Arc and London Arc, while continuing his pursuit of Wisteria. His perspective on Marbas gradually shifts as he understands Wisteria requires the demon's presence to avoid being sold into servitude. This leads to a reluctant acceptance of their bond, despite his inherent distrust of demons.

His abilities center on innate clairvoyance. Key relationships define him: protective devotion to Wisteria remains central, his partnership with Takenami involves collaborative efforts to locate her, and wartime connections with Luther Roosevelt and John Watson add complexity to his narrative interactions.