I think this story is one of the best in vn's. Even better than BaD. The dev creates his own post apocalypse society where powerful men can have wives and multiple concubines. That much is historically accurate. There have been such societies without consequences. It is also true that humans, after great calamities, tend to double down about the business of making babies. I don't see that in this game, nope not a lot of children.
But here there is no incest taboo. Everything goes, all in the name of bringing the family closer emotionally. It is true that the calamity in this game is beyond calamity, and humanity does not seem to be recovering very well. Does that mean humans would turn to incest in that situation? Well, the dev can say it does as well as not, since this is a brand new situation.
And it is true that humans have tried the incest route some, in royal families for instance, that refuse to bring commoners into the blood line. And, in that case, there have been consequences. Incest tends to breed idiots and monsters. That is the reason for the taboo. But, as I say, not a lot of kids in this game. And in cases where incest does not breed children, and there is no social taboo, why not?
Ok, I am going to get back into this great game. Love it, not that I am into incest, and no, adult incest is not the same thing as pedophilia. None of that in this game. There are a few games on f95 that present girls who appear well be below the age of consent and claim that they are 18 years old. Nope, not that either. Fair enough, I think.