A young boy, Sōsuke, befriends a strange looking goldfish whom he names Ponyo. Unbeknownst to Sōsuke, Ponyo is a magic fish who has decided that she wants to live with Sōsuke and the other humans. Unfortunately, Ponyo's decision to give up her underwater life creates a crack in an ancient magic spell, and places the world in danger. Together, Sōsuke and Ponyo must set things right.