Orphaned when hunters slaughter his parents and entire herd in Hokkaido's mountains, the baby deer Poyu is left frightened and alone until rescued by Kanta. Poyu possesses a unique golden tail, making him a distinct target for hunters and heightening his peril.

Under Kanta's care, Poyu matures from a vulnerable fawn into a brave young buck. Their bond is mutually transformative: Kanta finds courage protecting Poyu, while the deer exhibits resilience surviving Hokkaido's harsh winters and evading hunters. Their shared mission focuses on protecting the local deer population from extinction.

Poyu's struggle against human threats and extreme conditions symbolizes wildlife conservation themes, emphasizing the vulnerability of endangered species like the Ezo deer to human actions, particularly indiscriminate hunting. His dependence on human protection underscores messages about compassion for animals and ecological harmony.

In adaptations like stage musicals, Poyu sometimes gains magical qualities absent from core source materials. His role consistently serves as a catalyst for exploring interspecies friendship, the impacts of poaching, and nature's resilience when protected.