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.

Two high school nobodies make the decision to crash the last major celebration before the new millennium on New Year's Eve 1999. The night becomes even crazier than they could have ever dreamed when the clock strikes midnight.