Aria is alone on an Earth where the world has ended. Or rather it's her and her cat Jelly Beans. Sometimes she also narrates her life but it's just the two of them, some warring groups of humans, and her mission. Not an obviously rewarding one and her time there is not an easy one but she has one goal in mind: returning home.
It's a really odd world, so alike to our own and also not, and there's a lot of emptiness aside from one girl and her cat but that's really all the world we really need. It's interesting.