Ess is a curious and affectionate child around three or four years old who arrives on the island the same day Deen leaves, becoming Jinny’s Care. She shares a close, sibling-like bond with Jinny.

Jinny’s best friend, Deen leaves the island at the beginning of the novel but serves as a memory and guide for Jinny throughout the story. He believes in following the island's rules and becomes a source of inspiration for Jinny.

One year younger than Jinny, Ben is supposed to learn from her how to be an Elder. He is responsible, kind, and takes on many responsibilities, acting as a support for Jinny.

A girl close in age to Jinny, Joon is practical, quick, and resourceful. She helps lead the group and teaches Jinny valuable lessons about group dynamics and responsibilities.

A younger girl on the island, Eevie frequently questions the island's rules and sometimes clashes with Jinny. As a complex character, she resembles Jinny in her skepticism.

The youngest on the island before Ess arrives, Sam was Deen's care and is gentle, cooperative, and curious. He looks up to Jinny after Deen leaves, reminding her of her broader responsibilities.

Arriving on the island when Jinny's time to leave has come, Loo is noisy and adventurous. He tests Jinny's patience and skills as an Elder.

The name found in all the books left on the island, Abbie Ellis wrote notes in the margins that entertain and provoke thought among the children. Her presence raises questions about the island's purpose and the children's origins.