Barry uses his super-speed to have sex with Diana without her knowing it. From Barry's POV, Diana is pretty much motionless as he has his way with her, but from Diana's POV, she has sudden and powerful orgasms for no clear reason.
Bonus points if Diana begins to suspect Barry is responsible for her sudden orgasms.
Barry/Diana - Speed Sex, dubcon
Bonus points if Diana begins to suspect Barry is responsible for her sudden orgasms.