Yeah, in vast airtight geothermally heated caverns that don't yet exist, using a closed cycle ark-ship ecology that has neither been perfected nor really even s

Yeah, in vast airtight geothermally heated caverns that don't yet exist, using a closed cycle ark-ship ecology that has neither been perfected nor really even seriously tried, and with an "outside" that would be as ferociously hostile to human life as the surface of Pluto. Good anime setting, not really a plausible human future.