Shiro, also called White, is one of two central orphaned children surviving on Treasure Town's streets alongside his counterpart Kuro. He displays pronounced childlike innocence, frequently retreating into fantasy worlds, contrasting Kuro's streetwise toughness. Though eleven years old, Shiro's mental age seems younger, manifesting in struggles with basic tasks like dressing himself, yet he exhibits remarkable agility navigating the urban environment through parkour-like movements.

The orphans share an inseparable bond, calling themselves "the Cats" and claiming Treasure Town as their territory. Their relationship operates on a near-psychic level of interdependence: Shiro embodies purity and emotional vulnerability, relying on Kuro for protection and guidance. This dynamic proves crucial to both characters' stability, as Shiro's presence actively counterbalances Kuro's emerging violent tendencies.

During conflict with forces seeking to redevelop Treasure Town, Shiro suffers severe injuries when attacked by an enhanced assassin codenamed Butterfly. Authorities subsequently remove him from the streets into protective custody. This separation triggers significant deterioration: Shiro loses his primary emotional anchor, while Kuro spirals toward violent insanity without Shiro's grounding influence.

Following recovery, Shiro returns to Treasure Town to find Kuro psychologically fractured and hallucinating. Their reunion becomes pivotal when Kuro nearly succumbs to his destructive "minotaur" persona. Shiro's reappearance and intervention help Kuro overcome this inner darkness, restoring their fundamental connection. The narrative concludes with them playing together on a beach, their bond reaffirmed as essential to mutual survival and identity.

Shiro's character arc emphasizes thematic contrasts between innocence and corruption, exploring how vulnerability and dependence paradoxically constitute strength within transformative relationships. His journey illustrates the fragility and resilience of childlike wonder amid urban decay and violence, serving as an emotional counterweight to the story's darker elements.