I also thought the sameeee since the duke kept claiming his a virgin and then coincidentally his father's whereabouts are unknown and not his not dead,( probably looking for something or someone)and plus your theory also add up I think it isn't a theory anymore but a spoiler (≧∀≦)
I also thought about that and or maybe the duke just got hella drunk and he forgot that something happend to them but the girl immediately left in the morning so the duke thought that he is still a virgin or something ╮(￣▽￣)╭
But he said that he hasn't gotten drunk at all and avoided balls and parties so how did he get drunk? Plus if they did it and she left the in the morning, wouldn't the duke be naked or atleast have a hangover?
Amnesia could also be a case like maybe the memories are inside the pendant that the mc has and that is the key in knowing who her mother is
Hmm, well that could be a possibility except that they have to go to Count Zachary to take the pendant cause he was the one who gave it to the MC since she doesn't have it
That a really good theory. I was wondering what the importance the pendent had, beside that it is from her mother.
So, my theory is that the MC's mother is the Lady Orpheus that was mention in chapter 8. The abusive count said that the MC looked just like her. I think he meant MC's mother that he loved but was rejected by her. And I think, that is why he hates the Duke and talked shit about him to the MC, because Lady Orpheus was most likely in love with the Duke.
But this is just a theory ╮(￣▽￣)╭