About hormones, there's no hormones which will make any teenager to imagine their parent sexually.
I mean if the only person you know is your parent then you can maybe go that point. I don't say every teenager have sexual fantasies about their parents but some do.
I would say they would be disgusted with that thought (majority)
I mean if you just keep up that as fantasies i don't see the problem. It's when you went to go for it for real that it become a yikes.
You don't know what happened between them, so you can tell neither am I wrong because manga will show.
i don't see the author pulling such a dark and twisted story for the manga. It's already twisted enough to not add a drug uncousious sexual abuse.