This story has amazing potential. Overall, I love the plot and storyline although I do have some tips and suggestions. I believe a bit of background information is needed in the start of the chapter. This could be done by describing who is the man behind the seal and placing key sentences to explain why the woman even resides in the same building as him. You don't have to give his name right away if you want to keep the mystery, you can describe his status in the world of this story, why everyone fears him or what kind of creature he is, etc.
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I suggest this because I honestly felt very confused regarding the woman's place in the story. She felt terrified but loved the man's intentions (very rough handling) at the same time. I think the amount of fear the female character is showing does not match her liking or her lust towards the male character. I believe the level of fear can be toned down a bit and you can add how much or what she likes by the man's sexual intentions because I honestly perceived it as a sexual assault from the amount of fear she was showing. This probably wasn't your intention, or it isn't the case, but some readers may perceive it as such.
Some of the descriptions gave a medieval vibe, but it feels like there aren't enough descriptions of the setting and characters to reinforce this. For example, you could describe the stairs, maybe there are torches, maybe the door is made of thick wood; describing the character's clothes (example: long dress), describing the room where they meet, etc. I also recommend describing a bit more the physical appearance of the characters: is he pale, are his eyes pitch black without a single shred of emotion, is she tall or short, is she tan or pale, etc. If it is a medieval period you shouldn't use "He spins her around and pushes her against the wall as if she is being searched by the cops." because cops aren't relatable to the medieval period.
"He spins her around and pushes her against the wall, running his hands over her luscious sides." could be an option.
Another tip to remember is that normal dialogue doesn't need to be in italics; italics are generally used for thoughts. When describing it is best to show instead of telling; this also something I have been working on improving in my writing. Here are some examples:
"Her eyes grow big..." could also be, "Her eyes threaten to bulge from their sockets by the sheer pressure..."
"He grabs a fist full of hair and holds her head up..." could also be, "He grabs a fistful of her black tresses, forcing her to look..."
"After a quite a few thrusts, his cock wants to invade the second lips of a woman." could also be, "After a couple of thrusts, his cock throbs demanding to have a taste of her nether lips." or "After a couple of thrusts, his cock swells with the need to be squeezed by the warm walls of her c*nt."
"When he pulls out, her pussy makes an air sucking sound." could also be, "He comes out of her weeping pussy with a resounding pop."
I really like the plot of this story and I think it just needs a bit more work in the descriptions to make it really spark. Sorry for the very long review; I always try to be as helpful as I can be and honest with my reviews. I hope this review can be helpful to you; I have nothing against your story and I do not want you to feel offended nor discouraged by my suggestions. I love romance and erotic stories. If you have a Wattpad account, let me know; I think there are a few books I could recommend you. Keep up the awesome work!