The Raccoons of the Tama Hills are being forced from their homes by the rapid development of houses and shopping malls. As it becomes harder to find food and shelter, they decide to band together and fight back. The Raccoons practice and perfect the ancient art of transformation until they are even able to appear as humans in hilarious circumstances.

When Sosuke, a young boy who lives on a clifftop overlooking the sea, rescues a stranded goldfish named Ponyo, he discovers more than he bargained for. Ponyo is a curious, energetic young creature who yearns to be human, but even as she causes chaos around the house, her father, a powerful sorcerer, schemes to return Ponyo to the sea.