(This analysis concerns yesterday's story.)
I think it's the way he's lifted her dress. After that comes her leaning over him, supporting herself on his shoulders as he makes her feel she has no choice but to lean over, because she yearns to be claimed that way, yearns to be made to show what he can do to her with the merest touch, and the way he has the right to lift her dress that way, whenever he wants.
Then come the elegant dress, and her hair, and the barely-glimpsed scenery. Oh, and his chest.
But the central thermeme is the simple, dominant act of a man putting his hand up my dress, according to his desire. He finds that I am without underwear, because I must always be available to him. He has spanked me, of course--why wouldn't he? He likes to spank girls, and I am a girl who deserves spanking because I get so very wet whenever he calls me to him, so that he may lift my dress and claim his rights over my body.