In incest animu do you prefer it when they address how most of the world sees it as illegal immoral or do you prefer when they pretend that everyone's fine with it?
Both, because that makes it more interactive if you actually include all the points instead of just one side. They should go with their own side in the end anyways because love trumps all or something.
She still lapses back into 'Oniichan' when she wants sex.
How come Mikan was fine with Lala taking naked naps with Rito and whatever else but suddenly feels threatened when Momo starts doing the same thing?
Incest anime are about telling the rest of the world to piss off while you go pursue your forbidden desires. So, only a little bit, but don't devote too much time to it. Just enough to establish that it's generally frowned upon and will create major problems in the future, but have them bang anyways.