This was the start. Now that he knew Tony wanted him in return, Steve wasn't going to be able to stop. This was his chance and he needed to hold onto it with both hands, to learn to let down defences and let them have this. There were so many messes to make and Steve wanted to be there to clean them up as well.
Steve gripped his ass a little tighter and lamented for a moment that he wasn't naked and that he couldn't get a good look at him. But he would, nothing would keep that from him now. They were both coming unwound, Tony moved in his lap with determination and he rolled his hips again pushing up once more into the tight circle of his fist.
Tony came, the splatter of it up his stomach and it made things slicker and messy and Steve groaned before he joined him. "Tony," he gasped out.