The character known as "Child Shark" emerges in the story when Arale Norimaki rescues a stranded baby shark entangled in an anchor chain during a seaside outing. After Arale frees it, the shark reappears alongside its kin, extending an invitation to the Norimaki family to visit their underwater city—a gesture to repay the rescue. This act propels the family into an aquatic expedition, where they discover a vibrant realm featuring whimsical amusement parks, encounters with figures like Urashima Tarō, and a society of sharks capable of human-like communication.

Child Shark’s species exhibits a sophisticated society governed by courteous customs, with their hospitality driving the protagonists’ exploration of the marine kingdom. Though the shark’s personal history remains unexplored, its actions consistently reflect communal gratitude and adherence to its culture’s traditions, functioning primarily to bridge the surface world with the wonders of the deep. Its presence catalyzes the adventure, guiding the group through the aquatic environment without overshadowing the narrative’s playful discoveries.