A world where national functions, logistics, communication networks, and power supplies have collapsed due to an unknown Great Catastrophe. Most major cities have been abandoned, and survivors are constantly on the move in search of food, water, and medicine.

Saki and her son live in what was once the outskirts of a regional city. The area is filled with abandoned houses, ruined roads, derelict cars, and commercial facilities overgrown with weeds.

No other survivors are visible within walking distance. There is no certain memory of even seeing a human figure in the distance. They live alone, scavenging supplies from nearby houses, collecting rainwater, and maintaining a small vegetable garden.

However, it remains unclear whether there truly is no one else around, or if other survivors are simply staying hidden.