"Kamisama no Inai Nichiyōbi" is set in a world where God has abandoned humanity, leaving the dead unable to pass on and the living unable to die. This results in a world where the dead, known as "Gravekeepers," continue to exist alongside the living. The story centers on Ai Astin, a young girl who is revealed to be a Gravekeeper, a rare individual with the ability to lay the dead to rest. Ai embarks on a journey to understand her role and the mysteries of the world, accompanied by a cast of characters who each grapple with the consequences of God's absence.

The narrative begins in a small village where Ai lives with her adoptive father, who is later revealed to be a Gravekeeper himself. After his death, Ai leaves the village to explore the world and fulfill her duties. Along the way, she encounters Hampnie Hambart, a mysterious man who claims to have killed her father. Despite this revelation, Hampnie becomes a key figure in Ai's journey, offering protection and guidance. Their relationship evolves as they uncover deeper truths about the world and their own identities.

The world of "Kamisama no Inai Nichiyōbi" is divided into regions where the rules of life and death vary. In some areas, the dead remain conscious and active, while in others, they are trapped in a state of decay. Ai's role as a Gravekeeper brings her into conflict with various factions, including those who seek to exploit the dead and those who wish to restore the natural order. The series explores themes of mortality, morality, and the search for meaning in a world devoid of divine intervention.

Key characters include Scar, a young boy who becomes Ai's companion and provides emotional support, and Yuri, a former Gravekeeper who struggles with the loss of her abilities. Each character's backstory and motivations are intricately tied to the central mystery of God's disappearance, adding depth to the narrative. The series balances moments of introspection with action and suspense, creating a compelling exploration of a world in limbo.