Asirpa is a young girl belonging to the Ainu tribe, an indigenous people of Japan, and she serves as a central figure in the narrative. Physically, she has a petite and small frame, with long dark hair and distinctive blue eyes that have hints of green. Her typical attire consists of a traditional white Ainu robe made from attus bark fiber, decorated with swirling patterns, which she wears over a purple kimono. She completes her outfit with dark leggings, deerskin boots called yukker, and a wolf fur mantle for protection against the harsh cold. Asirpa also wears several important accessories, including a purple embroidered headband known as a matanpushi, matching hand coverings called tekunpe, and two ninkari earrings that were an heirloom from her mother.

Asirpa's personality is a blend of maturity and youthful spirit. As a skilled huntress, she possesses a deep, pragmatic understanding of nature's cruelty, knowing that weakness leads to death in the wilderness. This makes her serious and focused when hunting or pursuing her goals, and she can initially appear cold or unforgiving to those she does not know. However, once she warms up to a person, she reveals a more jovial, spirited, and cheerful side. She has a notable enthusiasm for food and cooking, often becoming obsessed with eating and catching prey. She is generally friendly and polite, especially to elders, but is more familiar and playful with her close companions, whom she occasionally teases. Asirpa holds a deep reverence for Ainu culture and nature, viewing animals as divine beings called kamuy. She always honors her prey and uses every part of the animal, believing it to be a gift from the kamuy. As such, she refuses to eat the meat of a man-killing animal, which she considers a wen kamuy, or evil god. While she respects her heritage, she also considers herself a new kind of Ainu woman and dismisses some customs, such as tattooing her mouth or believing in fortune-telling.

Her background is marked by the death of her father, a tragedy that left her withdrawn and dependent on her pet wolf, Retar, for emotional support. For a long time after this loss, she rarely smiled. This changed when she met Sugimoto, a Japanese war veteran searching for a hidden stash of Ainu gold. Asirpa's primary motivation is to find the gold not for personal wealth, but to protect her people and preserve the Ainu way of life from the encroaching forces of modernization and Japanese imperialism. She fears that without the gold, the Ainu culture and independence will be erased or forgotten.

In the story, Asirpa is the deuteragonist, whose skills are essential for survival in the Hokkaido wilderness. She saves Sugimoto's life early on, and after learning the story of the hidden gold that was stolen from her people, she agrees to partner with him. Her role is to guide him through the land, using her extensive knowledge to hunt, cook, and navigate, while he provides military and combat experience to fend off dangerous enemies. Her ultimate goal is to find the man responsible for her father's death and reclaim the Ainu treasure.

Asirpa's most significant relationship is with Sugimoto. Their partnership, built on mutual respect and trust, is the heart of the story. Through their journey together, she regains her smile and playful nature. However, she also struggles with a lingering fear of being abandoned, worried that Sugimoto might leave once they find the gold. She has other key relationships as well, including with her uncle Makanakkuru, who notes how her friendship with Sugimoto has brought back her joy. She also works alongside allies like the former convict Shiraishi and the Russian revolutionary Kiroranke.

Throughout the narrative, Asirpa undergoes significant development. She transitions from a withdrawn, serious girl to a more open and emotionally expressive young woman, largely due to her bond with Sugimoto. Her initial goal of revenge evolves into a more complex and mature desire to secure a future for the Ainu people. She becomes more determined to use the gold as a tool for cultural preservation rather than simply as a means for vengeance.

Asirpa possesses a wide range of notable abilities. She is a highly skilled huntress, trained from a young age by her father. Her skills include trapping, brewing poisons, archery using her longbow, and a deep knowledge of Hokkaido's flora, fauna, and traditional medicine. She is also an excellent cook, capable of preparing many traditional Ainu dishes from the animals she hunts and plants she forages. Despite having little formal training, she is a good artist, as shown when she copies the tattooed maps of escaped prisoners onto paper. Her equipment reflects her lifestyle, including a hunting knife, snowshoes, a deer whistle, and various tools for survival in the winter.