Most of the Sins aren't going to rape Maria at all. Asmodeus is only doing it because she's the personification of lust, and whatever interaction Leviathan has with Maria will be a consequence of jealousy.
Yeah, sure. Down the road they're going to unveil some contrivance to make Maria related to Lucifer but that won't make Maria contribute to the plot or be interesting. Characters that contribute something to the cast do so on their own merit, not because they've some elaborate relation to the MC. That's bullshit and an excuse to cram white-noise characters.
Look, I'm just salty because there's 9 demons with great designs and at 2 episodes in, 90% of the show's time has gone to the same two demons, and a vanilla human. Where's the screentime for Mammon? What about Belphegor, Gluttony, and Beelzebub? We haven't even seen Astaroth. All the time is going to Leviathan, (who is great so no complaints there), Lucifer, and Maria. I expect Luci will be better later on too but she was and annoying child in the first episode. The best thing about her is Levi.
So basically this just feels like a tremendous waste of potential and I'm angry.