Haro Amuro, a male Hokkaido dog, roamed as a stray until discovered injured, bearing fresh cuts and bruises. His persistent shadowing of Rei Furuya led to reluctant adoption after Rei remembered Elena Miyano, a biochemist from his childhood who once nurtured him. The dog earned his name when Rei noticed his tail-wagging response to guitar notes "Ha" (C) and "Ro" (B), following an incident where Haro toppled the instrument. This prompted Rei to strum "Furusato," a melody taught by his deceased friend Hiromitsu Morofushi (Scotch), intertwining past and present.

Haro’s mischievous pranks—overturning household items or darting from vet clinics—clash with Rei’s rigid routines, gradually softening the man’s stern exterior. During a chaotic parade, Rei balanced rescuing a kidnapped infant with corralling the excitable dog. Later, a cherry blossom outing saw Haro disrupt Rei’s somber reflections, symbolizing a fragile link between the agent’s trauma and newfound camaraderie.

Subtle cues tie Haro to Rei’s unresolved grief over Scotch’s death and his tense dynamic with Shuichi Akai, as the dog’s presence quietly steers Rei toward fleeting moments of peace. Through loyalty and spontaneity, Haro embodies the fragile coexistence of conflict and connection in Rei’s life.