this is actually such a great theory
I think it was confirmed at the beginning that her dad was an angel and that's why she got a guardian angel. we don't know about her mom but I like your theory, I didn't realise that she could be a demon and now that I read your comment, I notice more subtle hints. also the fact that she is somehow special could indicate that her parents were somehow not just a "regular" couple. I'm really curious to see how it turns out. BTW it might be a little bit off topic but I was thinking about another theory. The MC had flashbacks of the memories with Doya from the past. I think that the MC might be the reincarnation of that girl?? but at the same time I'm not sure but what's the other reason why she saw that? maybe that's because of her power? OH WOW that would be interesting lol sorry for such a long reply, it's nice to see someone who isn't only horny but also looks forward to the plot (tbh this webtoon is more interesting than I thought and actually has some plot)
Oh? I forgot about the beginning and glazed over some texts so I didn't know about the dad thing actually being confirmed..i was also thinking that this would be just some short fun smut (I mean!! It's rare to see actual plots nowadays in regards to smut) anyways!! I do agree with your theory and I'm also pretty sure that she is the reincarnation of the lady in the past in doya and seowon's dream. The fact that doya gets horny with the touch of seo won just proves that they indeed had some connection. I also reread some chs from the beginning with hints from doya's "uncle" erasing some of his memories (when he asked how to erase the rumor about jaehyun and seowon at ET) but not all of it can be erased and some fragments may show up thus doya dreaming about his past which he thinks is just a dream.
Ok, setting aside the seo doya and woo jaehyun debate, I'm actually curious what type of supernatural mc is? doya mentioned getting sick during winter and her remembering that her mother was like that too? The backstory about her father is also shrouded in mystery. Since she has a guardian angel...I'm thinking that the father is an angel and after the father passed away(?) or left(?) them, he intentionally placed a guardian angel to guard MC and her mother is actually a demon so she's some sort of mixed breed?? Her mother's ears are covered and the demons on this manhwa just have black hair....also the fact that her mother gets sick during the winter just suggests that her mother is indeed a supernatural...anyways what do y'all think.