Anime: Wonderful Days

"How long has it been raining? Forever. Not forever, no! For a hundred years. They say billions of people once lived on the Earth. When the temperatures rose, the great cities fell, and this rain came, this terrible toxic rain. Our ancestors saw it coming, the catastrophe. They built Ecoban, the first living city, genetically engineered to survive in a poisonous environment. Ecoban became our refuge, our salvation. Survivors came by the thousands, begging to be let in. But our ancestors turned them away, left them to die in the wasteland. The ones who survived became our workers, mining the carbonite fields to feed our Ecoban. Diggers we call them. The Diggers need us, we need them, everybody wins. But some win more than others."