Morimura Aiko is a junior high school student who is short for her age. Her father departed on a yacht ten years ago, and his whereabouts remain unknown. Her mother, a hat designer, left for Paris, leaving Aiko in the care of her uncle, Mr. Fujinami. Aiko had a pet dog named Papi, but he died in a car accident. Around the same time, another dog, Spank, appears before her. Having endured so many unfortunate events in her life, Spank's presence begins to brighten Aiko's life and put a smile on her face.