Sosuke, a five-year-old boy with a bowl-cut hairstyle and sun-kissed skin, lives in a cliffside coastal village. His father, Koichi, works as a frequently absent sailor, while his mother, Lisa, tends to elders at a care facility. Born on May 25, 2003, he favors a yellow short-sleeved shirt and dark grey shorts, typically roaming barefoot or in uwabaki slippers. While exploring the shore, Sosuke discovers a goldfish trapped in a glass jar, rescues her, and names her Ponyo. A small cut on his thumb during the rescue bonds them when Ponyo heals the wound with a lick. He hides her first in a bucket, then in nursery school bushes to shield her from classmates like Kumiko. His anguish over Ponyo’s abduction by her father, Fujimoto, underscores their profound connection. When Ponyo’s magic triggers a cataclysmic storm, floodwaters engulf Sosuke’s home. After Lisa departs to aid elderly neighbors, he voyages with Ponyo in a magically enlarged toy boat. Navigating submerged landscapes, he perseveres through her energy dips and temporary reversion to fish form, steadfastly pushing their vessel ashore and carrying her when needed. Confronted by Fujimoto’s warnings of ecological chaos, Sosuke resists capture yet reaffirms his loyalty to Ponyo. Meeting her mother, Granmamare, he vows to accept every version of Ponyo—declaring love for “all the Ponyos”—which restores balance and finalizes her human transformation. Curious and compassionate, Sosuke balances marine-life fascination with a protective streak, diligently feeding Ponyo and defying threats to her safety. His interactions with adults blend deference with resolve, particularly when defending Ponyo’s choices. Inspired by director Hayao Miyazaki’s observations of his five-year-old son, Sosuke’s design captures childhood authenticity. His journey explores trust, humanity’s coexistence with nature, and boundless love, cementing his role as a mediator between mundane and mystical realms. The character remains exclusive to his original film narrative.