Blanc, nicknamed White, is an orphan surviving on the streets of Treasure Town with his inseparable counterpart, Noir. Together, they rule as the delinquent pair known as "the Cats," claiming the city as their territory. Blanc displays a childlike innocence, frequently escaping into rich inner fantasies that starkly contrast Noir's hardened street smarts. This innocence fuels a persistent cheerfulness; he constantly repeats mantras like "Be happy" and "Don't worry," a clear coping mechanism. This demeanor potentially hints at underlying cognitive differences or trauma stemming from his homelessness and lack of parental guidance.

Blanc serves as Noir's essential emotional anchor, counterbalancing Noir's violent impulses. Their relationship is deeply symbiotic: Blanc depends on Noir for physical protection, while Noir needs Blanc's innocence to retain his humanity. When authorities take Blanc into custody after a near-fatal stabbing, their separation triggers a psychological collapse in both. Noir spirals into violent madness, manifesting a destructive alter ego called the Minotaur, while Blanc loses his grip on reality. Blanc's eventual return proves vital for Noir's redemption; his unwavering affection and refusal to abandon Noir empower Noir to reject the Minotaur's control.

Despite his gentle core identity rooted in compassion and optimism, Blanc demonstrates surprising capacity for violence defending his brother, notably killing an assassin in self-defense by setting him alight. His vivid imaginative visions often depict idyllic escapes like an ocean paradise or an apple tree, representing hope and acting as a shared mental refuge. These visions find physical form in the story's conclusion: the brothers reunite on a beach, and an apple seed Blanc planted earlier sprouts, symbolizing renewal and their restored bond.

Blanc possesses extraordinary physical abilities, including advanced parkour skills enabling effortless navigation of rooftops and urban structures. These unexplained capabilities align with the film's magic realism. His journey embodies themes of innocence vulnerable in a harsh world, yet also possessing redemptive power. His arc culminates in reaffirming the brothers' interdependence, showcasing love and mutual need as sustaining forces against urban decay and internal darkness.