"Listen here. I have half a dozen blades to finish tempering and two more sets of plate armor to finish adjusting before the morning, and you think I have time to work on an unknown sword with an unknown alloy for someone that doesn't even know my prices? You may be a Titan, but you're still mortal just like the rest of us. You can wait your damn turn."
Blacksmith Tony Stark is the best in the business, and he doesn't take well to being talked down to. When what should have been a single job for a passing Titan becomes something more, his whole life gets turned upside down.
A battle gone wrong leads Tony to the unexpected and pleasant discovery that Steve is much more well-endowed than he could ever have imagined. But when Tony learns that Steve has never actually been able to sleep with anyone because of his size, Tony does what any good friend would do: he offers to relieve Steve of his virginity. Personally. Tony's determined, Tony's methodical, and Tony has a plan. He's going to get Steve laid. Tony just needs to make sure Steve never finds out that Tony's in love with him.
He let his hands rest, warmly, on Steve’s shoulders, against his neck. “I just want you to fuck me, soldier,” he managed to get out, breathy. “I want you to fuck me, yes, in my ass, and not stop. Again and again, until it’s out of your system.”
Steve and Tony and a marathon sex encounter. That's it, that's the fic.