Hina is a young child living in Tokyo with her brother Hayato. She has pigtails and a distinctive hair antenna. Discovering a blue feather on the road sparks her curiosity about its origin, leading her to search for its owner. A mysterious crow named Karasu appears to guide Hina, Hayato, and their quest. Together, they travel and encounter various birds while tracing clues about the feather's source, focusing on identifying which bird it belongs to.