Asirpa is a young Ainu girl who serves as a central figure in the hunt for a hidden treasure in Hokkaido. She is introduced as a skilled huntress living a traditional life in the wilderness, possessing deep knowledge of the land's flora, fauna, and survival techniques. Her father, a respected figure in their community, was killed under circumstances connected to the stolen Ainu gold, a loss that initially left her withdrawn and solitary. After saving the life of a Japanese soldier named Sugimoto, she learns of his quest to find the gold and agrees to partner with him, providing her expertise in exchange for help in uncovering the truth about her father's death.

Asirpa is defined by her independence, capability, and a personality that balances seriousness with youthful playfulness. Initially, she can appear cold and distant, but this quickly gives way to a more jovial and cheerful side once she grows comfortable with someone. With her companions, she is playful and enthusiastic, especially about cooking and hunting, and she often teases Sugimoto and another ally named Shiraishi. However, her life as a hunter has instilled in her a pragmatic and mature understanding of nature's harsh realities, where weakness leads to death. Despite this pragmatism, she adheres to a strict personal code, refusing to take human life even when her own is in danger. She deeply respects Ainu traditions and the belief that animals are kamuy, or gods, which leads her to always honor her prey. At the same time, she considers herself a modern Ainu woman and is not afraid to dismiss certain customs, such as tattooing her mouth or adhering to superstitions like fortune-telling.

Her primary motivation evolves over the course of the journey. While initially driven by a desire for answers regarding her father's murder, her experiences traveling across Hokkaido and beyond to Karafuto broaden her perspective. She becomes driven by a greater purpose: to protect the Ainu people and preserve their culture and independence from being erased or forgotten. She sees the legendary gold as a means to secure this future for her people. Her relationship with Sugimoto is central to her development. Her uncle notes that she rarely smiled after her father's death until she befriended Sugimoto, who helped her find her smile again. However, she also struggles with a lingering fear of being abandoned, uncertain if Sugimoto will stay by her side once their goal is achieved. Her other key relationships include her uncle Makanakkuru, her grandmother Huci, and the escaped convict Shiraishi, with whom she forms a close bond as part of their group.

In the story, Asirpa acts as the group's guide and survival expert. She is responsible for hunting, trapping, cooking, and navigating the harsh Hokkaido winter. Her skills are vast, including archery, brewing poison from aconite for her arrows, creating traps, preparing traditional Ainu cuisine, and possessing an encyclopedic knowledge of medicinal plants. She is also an artist, using her drawing skills to copy the intricate tattooed maps found on the bodies of escaped prisoners. As the narrative progresses, she matures significantly, and by the end of the story, several years later, she has grown considerably, standing nearly as tall as Sugimoto's shoulder, a physical representation of her personal growth throughout the series.