Sosuke is a 5-year-old boy who lives on a cliff. One day, he rescues a strange looking goldfish and names her Ponyo. He takes a great liking to her and promises to protect her forever. Unknown to him, Ponyo is a magic fish and she decides that she wants to live with Sosuke. Unfortunately, Ponyo's decision to give up her underwater life upsets an ancient magic spell and places the world in danger. Together, Sosuke and Ponyo must set things right.