Are there any of your monsters that immediately mentally lay claim to the human? Like just immediately decide yes I want
Jelly is definitely one of those monsters! The first moment you meet she'll be planning out your future together in her mind. She can be incredibly possessive over what she sees as hers and will take any and every opportunity for bonding--and like it or not, you're her spank bank material from then on. She'll get a sex toy (or have Lydia's contact in the Underworld custom make one) that resembles you to get off with, because from then on it's just you, you, you. You're all she thinks about and all she wants. But she's not submissive about it, rather she's kind of bossy, like she wants you to understand that she doesn't just need you but that you're meant to be together in some way. She can be just friends, that's possible, but she'll be your best friend and just hide the sex stuff from you as best she can. If romance isn't on the table she'll be more like your bodyguard, intent on protecting you from any evil even if it hurts her. And if you just want a hookup, she can do that too--besides, the venom off those little tentacles is just intoxicating when she stings you right on the brink of your climax. Either way, there's a part of her that can never be normal again after she meets you, and to be honest she really prefers it that way.