We've Done this Before (as Mars Sauntered Through His Door) (слэш)

“Why’re you awake?” Steve wonders out loud.
“I don’t have what anyone would call regular sleeping habits,” Tony says, lips curling a little. “There’s some stuff in the workshop I want to get done.”
“Mmm,” Steve says. “You could have gone.” He’s pretty sure he means it; he’d half expected to wake up alone this morning anyway.
“I wanted a look at your back,” Tony says.
Steve wriggles over onto his front. The lights brighten a little in the room, and Tony’s hands slip easily down his back, and then flip the covers down so that he can continue down Steve’s ass.
“I don’t know if I’m disappointed or excited,” Tony says.
Steve makes a noise of agreement. “Walking around with the marks under my clothes would have been...” he says.
“I know,” Tony agrees. “But this way, there’s almost no wait time between wanting and doing.”
Steve makes another lazy sound of agreement.