A 17-year-old Japanese high school girl survives as the last human after an unspecified apocalypse. Previously a shut-in, she isolated in her room with her dog. Her personality blends cynicism and impulsiveness, often resulting in thoughtless or mean behavior towards others, including her canine companion; she openly prefers cats. Physically typical for her background, specific details are sparse. She reacts impulsively, like pinching her dog's face when annoyed by his remarks. Despite her flaws, she adapts skillfully to the desolate landscape and forms connections with non-human entities. Her personal history remains limited beyond her reclusive past.

Her development unfolds while traversing Japan's ruins. She gradually bonds with diverse entities: retired aliens she sometimes mooches from, mythological creatures like kitsune and kappa, and other animals. These encounters showcase her pragmatic survival instincts, such as binge-drinking alcohol discovered in abandoned places. The relationship with her dog evolves on their journey, revealing subtle hints of growing mutual dependence and affection beneath their comedic dynamic. Bonus content exploring their origin depicts her discovering him as a puppy in a rainstorm and reluctantly choosing to care for him.

Later experiences include attending a barbecue with Anubis and Bastet figures, navigating a haunted mansion alongside a group of dogs, and encountering an angel and a penguin. These events continue to highlight her cynical yet adaptable nature, exemplified by using practical solutions to counter supernatural threats during the haunted mansion incident.