Shiro is a devoted black cat whose profound affection for her human family drives her to seek greater ways to help them. Frustrated by her feline limitations, she makes a wish to the moon. Luna, recognized as the world's "prettiest cat" and Shiro's mother, responds by granting her a magical item that transforms her into a human girl.

In her new human form, Shiro retains energetic and impulsive feline traits. Her unfamiliarity with human social norms leads to chaotic situations, like overwhelming shop employees during an urgent Christmas gift search and inadvertently complicating things for her "Papa." She similarly intervenes with unrestrained enthusiasm upon learning her friend Satoko desires romance. These actions consistently stem from Shiro's earnest drive to support those she loves, despite frequent unintended consequences.

The narrative follows Shiro adapting to her temporary human existence while striving to orchestrate a unique Christmas celebration. This event aims to unite her human family and feline companions, embodying her goal of fostering harmony between her dual worlds. The documented story concludes with this Christmas event.