James is a seven-year-old orphan who is sent to live with his aunts after his parents are killed by an escaped rhinoceros. For three years, he suffers profound loneliness and physical mistreatment, longing for the companionship he once had. Despite his severe hardships, he retains a natural intelligence, curiosity, and an open heart toward others.

Spiker is James's tall and lean aunt who wears steel-rimmed glasses. She wrongly considers herself gorgeous while repeatedly belittling her nephew. She dominates her sister and immediately looks for ways to profit financially when a giant, magical peach appears in their barren garden.

Sponge is James's short, round aunt. Like her sister, she is highly narcissistic and dreams of being a glamorous movie star, though she spends her days sitting lazily in the garden while James completes arduous chores. She acts impulsively and frequently issues cruel punishments without reason.

The Centipede is a human-sized insect who wears lace-up boots on his forty-two feet. He thrives on being loud, singing raucous songs, and proudly identifying as a pest. His cheeky energy often lightens the mood for the group inside the peach, though his mouthiness occasionally causes unnecessary trouble.

The Earthworm is a blind, human-sized worm with smooth pink skin. He expects the worst from every situation, even when there is no immediate danger. Despite his gloomy outlook and habit of complaining, he participates in the group's survival efforts and secretly cares for his friends.

The Old-Green-Grasshopper is a large, short-horned grasshopper who serves as the elder statesman of the insect crew. Cultured and polite, he plays his own body like a musical instrument to entertain the group. He takes an immediate liking to James and offers him respect and validation.

The Ladybug is a giant insect belonging to the Nine Spotted Ladybug family. She possesses impeccable manners and immediately adopts a maternal, protective role toward James. She ensures that he feels safe and included from the moment they meet.

Miss Spider is a large black spider who spins durable silk. Though her initial appearance frightens James, she is deeply caring and often sheds tears when remembering her deceased family members. She considers herself a misunderstood helper of the natural world.

The Glow-Worm is a wingless female firefly who provides illumination for the travelers inside the dark peach stone. She is quiet but affectionate, glowing brightly when she is happy and greeting newcomers warmly.

The Silkworm is the quietest member of the giant insect crew. She rarely speaks and prefers to stay in the background, but her ability to rapidly spin immense amounts of silk proves critical to the group when facing dangerous obstacles.

The Old Man is a small, bald figure with bristly black whiskers. He intercepts James during a moment of profound despair, gifting him a bag of magical crocodile tongues and giving him instructions on how to change his life.