Shapeshifters who start out human-looking but lose the concentration and turn into a monstrous form while fucking a human <3
They are deep inside when their dick gets bigger, starts moving on its own like a human one can't, but both partners are too horny to notice. And then the whole facade cracks, face turning into maw, kisses into bites drawing blood, hands gently in hair into tentacles holding struggling arms in place. A hookup turning into breeding a helpless prey <3
Fun with both a terrified human who thinks this thing is gonna rip them to shreds or a monsterfucker character who is straight up high and instantly addicted to the monster's massive dick and the tounge literally in their throat
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