Don't worry, Ponyo. No matter what, I will protect you. I promise. - Sōsuke promises that he will protect Ponyo.
Sosuke is intelligent, smart, loyal, cute and heroic. He is willing to protect his friends (including Ponyo, starting from when she washes up on the shore near the house, stuck in a glass jar), even if doing so gets him in trouble with his mother or Ponyo's father (whom they hate). He is interested in the sea, especially since his father, Koichi, is the captain of a ship. He also knows that Koichi does his best for the family, as seen when Lisa gets angry at Koichi and chides him for abandoning her family on a cliff.
Sosuke is a 5-year-old boy who wears a sunshine yellow t-shirt and chocolate brown shorts. His hair is walnut brown with his hair shaven underneath. Also, he wears a sailor hat and binoculars.
Role in the film
Sosuke is first seen when Lisa calls Sosuke to come back home and he discovers Ponyo.
Sosuke is a 5-year-old boy and loves Ponyo in her human form.
Sosuke uses his toy boat and green bucket until Ponyo came back in her human form along with a sailor hat and binoculars.