The opening scene is a masterpiece. Any husband lucky enough to come home and find his wife half asleep in this condition will do exactly what this guy did (although the bedroom won't be as nicely lighted): admire and be totally turned on, and full erection is instantaneous. It doesn't really matter who fucked her, she's beautiful, sexy, and erotic and even more so now, full of another man's sperm. She will wake up as you gently spread her legs and slide deep inside her. There's no need for words. She's fertile, he's fertile, - This is what you both wanted so how he can pull out at the end is beyond me.