Brunhilde is a fish-girl who lives in an aquarium with her father Fujimoto, a wizard, in his underwater castle with numerous smaller sisters. One day, when her father takes her and her siblings on an outing in his four-flippered submarine, Brunhilde is driven by a desire to see even more of the world and floats away on the back of a jellyfish. She ends up stranded on the shore of a small fishing town and is rescued by a boy named Sōsuke, who cuts his finger in the process. She licks his wound when he picks her up, and the wound heals almost instantly. After taking a great liking to her, Sōsuke names her Ponyo and promises to protect her forever. Meanwhile, Fujimoto is looking for his daughter. Upset that she ran away, he believes the humans have now kidnapped her, and he calls his wave spirits to return Ponyo to him. After the wave spirits take Ponyo away, Sōsuke is heartbroken and goes home with his mother, Lisa, who tries to cheer him up, to no avail.