Marrybell wa Shinda to Papa ni Tsutaete

The story is told from the points of view of the six 'family members', who are all people who were dropped into this new world when their section of Tokyo 'fell'. They are also the only survivors... and they find themselves indebted deeply to the indigenous city that manage to reach and the merchant guild that sells them their house. A great deal of the story is about a combination of simple financial struggles to make ends meet and pay off more of their debt... and of how the various characters adapt - or don't.

[From Fuwanovel]