The entire narrative builds towards Junpei's transformation, which culminates in the film's quietly shocking ending. After living in the pit for a long time, a strange opportunity arises: the woman suffers an extrauterine pregnancy and must be urgently taken to a doctor. In their haste, the villagers leave the rope ladder behind, giving Junpei his long-awaited, unobstructed chance to escape. He climbs out, sees the ocean, and is physically free.
However, he glances back at the pit and his water-collecting device, which he has perfected. He realizes that he wants to tell someone—preferably the villagers—about his discovery. He decides that he can think about escaping the next day. He willingly descends back into the pit. The hidden meaning, which becomes clear in this moment, is that his internal landscape has completely changed. The drive for physical freedom has been replaced by the intellectual satisfaction and sense of purpose his invention has given him. He is no longer defined by his opposition to the villagers but by a newfound identity as a creator and discoverer within their world.
A final title card reveals a missing person's report for Niki Junpei, filed seven years prior, declaring him officially dead. This official document from his old world underscores the totality of his disappearance and the birth of his new existence. The man he was is legally and figuratively dead. He has been fully absorbed into the world of the dunes, not as a prisoner, but as a resident who has found a new, albeit absurd, reason to live.