Her weight, her warmth, her suppleness, her embrace, her kiss, her breath, and her heartbeat are on top of him. What can I say? I just like upright straddles.
I'm imagining the mental and physical space they're in to be emptied of unnecessary noises. There is nothing else but each other. You can hear a pin drop, so every sensation and reaction will be so crystal clear.
Reality Marbles exist in Fate, so imagine a magic user being able to create something like that for sex...