Niki Jumpei is a 31-year-old schoolteacher and amateur entomologist seeking to discover an unrecorded beetle species to earn the right to name it. He feels dissatisfied with the repetitive nature of his career and relationships, viewing his scientific hobby as a temporary escape from his daily obligations. Analytical and rational, he initially approaches the unique architecture of the sand village with detachment and a sense of superiority over the local residents.

The Woman is an approximately 30-year-old resident of the seaside village, living alone in a decrepit shack at the bottom of a deep sand pit. She spends her nights engaged in the exhausting labor of shoveling sand to prevent it from burying her home and the community. Despite her grueling existence and the loss of her immediate family, she demonstrates a resilient, practical connection to her village.

The Old Man acts as the de facto leader and spokesperson for the seaside village. Shrewd and observant, he operates the logistics of the community's survival, orchestrating the sand-hauling operation and monitoring those in the pits. He uses basic necessities like water and communication as leverage to ensure compliance from the village's captives.

The Möbius Man is a colleague of Niki Jumpei back in the city. He serves as a philosophical sounding board for Niki's frustrations regarding their teaching careers. He views labor as an exercise in self-denial, an ideology Niki wrestles with while trapped in the dunes.

Niki Shino is Niki Jumpei's mother, living in the outside world. She represents his remaining familial tie to conventional society and the bureaucratic system that tracks his disappearance.

A woman from Niki Jumpei's life in the city with whom he shares a complicated romantic arrangement. She demands unprotected intimacy while he insists on using precautions due to a venereal disease, leading to mutual resentment and emotional distance.

A coworker of Niki Jumpei who dabbles in psychoanalytic theory. He posits that entomology attracts individuals struggling with abandonment issues or a longing for death, suggesting suicide as the cause of Niki's vanishing.

A traveling postcard dealer who was previously trapped by the village to shovel sand. He died from illness while enduring hard labor during the dangerous typhoon season.

A student who came to the village to sell books and remains trapped there. He continuously works to haul sand, serving as proof that the village operates a larger network of captivity.

The former husband of The Woman. He and their daughter died in a sand avalanche during a typhoon the previous year, leaving The Woman to shovel sand alone.

The young daughter of The Woman, who perished in the same sand avalanche that claimed her father.