Story takes place in your run of the mill hicksville town out in the boonies where everyone knows your name and kids make youthful memories all year round - it's just that it's the very last of its kind and the last remaining humans outside of the town's containment bubble are fighting to keep its denizens happy and unaware of the war raging on the outside. Happy and unaware is the key here because their happiness is literally powering their tech.
Decades ago, first contact was made and an invasion began that resulted in mass abductions as humans apparently make for prime psychic power generators because of their social tech advancements. The human race managed to reverse engineer such generators and figured out how to make them work humanely but the damage done was too deep to turn things around. That's where the ark plans came in - isolated populations with socieities simulated to match the conditions of early 21st century to generate power for these bunkers.
As far as ground ark Hope Creek is concerned, they are the last free survivors on earth since it's been years since they've heard anything from the other stations. The struggle to maintain the facade and satisfaction levels is just as important as the bloody battles taking outside the town but now a major threat has appeared in the form of a precocious little boy who's noticed something's up - the world is not what it seems and he's going to make that clear to his beloved hometown.
I think this came about when I was rereading Mizukami's Walking the Void oneshot. Don't remember what I had in mind for the ending though but the twist is that there's only one proper living human being left outside the town protecting the rest with the help of AI automatons, that he'd turn out to be the kid that went missing years back and that it was his fault that the original caretakers got killed. As I wrote this up, I'll throw in a new twist where it turns out the AI automatons are actually the remnants of the enemy as the rest of his kind decided to leave and he got stranded with this ark being his only source of sustenance and it leads to how they decide to proceed forward.