AUTHOR'S NOTES: For context, since this ficlet is a piece out of a larger story that might never get written entirely: Tony and Steve have never been lovers when this story opens. Not even before Tony changed.
Steve drew Tony down onto the bed next to him and pulled him close with an arm around his waist. Tony came into his embrace easily, letting Steve's gentle hand cupped around the curve of his skull guide him in close to lay his lips on the column of his throat. Steve made sure to keep his breathing even and calm; even after nearly a month, Tony was still skittish about this. The reactions Steve was keeping such a careful leash on--pounding heart, quick breath, tense muscles--had nothing to do with fear, but he knew Tony would read it that way if Steve let go too soon.
So he controlled himself carefully and brought Tony close against his body, and when soft lips brushed his throat, he murmured, "It's okay. Go ahead."
There was a hot, trembling puff of breath against Steve's skin and then two tiny points of pain pierced him. Steve caught his breath. Not from the pain; it was hardly more than a pinprick. It was the sudden connection as life literally flowed from his veins and into Tony. Steve closed his eyes, letting go of his control now, letting his heart pound and his breath stagger, immersing himself in the sensation of a part of him flowing soul deep into Tony and spreading warmth and feeling through him.
Tony's tongue flickered against Steve's skin as he drank and Steve caught a moan in his throat, his hand flexing against the small of Tony's back.
It didn't last, of course. Eventually Tony had his fill and let his fangs slide from Steve's throat, nuzzling there and licking softly at the small wounds instead. Tony never seemed entirely aware of himself just after feeding. He was always deeply relaxed, almost to the point of sleep, which was why they'd taken to doing this lying down.
It was infuriating, sometimes, to have Tony sprawled so warm and pliant and sated against him when Steve was so damned excited.
Steve sighed, and winced at how loud it came out.
Next to him, Tony tensed and pushed himself into a sitting position. "I can't," he said tightly.
Steve closed his eyes and cursed himself roundly for a moment. Then he sat up, too. "You won't," he corrected.
"We hardly know anything about what I've become," Tony said harshly. "Who knows what I might do to you in the middle of sex?"
"I'd kind of like to find out what you'd do to me during sex," Steve said dryly.
Tony didn't laugh. "You know what I mean. I have instincts I don't understand."
"You've never hurt me."
Tony set his jaw. "And I'm not going to."
Steve laid a hand on Tony's back. "No, you aren't." He leaned in, tilting his head to kiss Tony.
Tony pulled away. "I'm not human anymore, Steve. You can't behave like I'm the same person."
Steve didn't try to kiss him again, but he didn't pull back either, instead speaking to Tony from less than an inch away. "Your heart's the same. Your soul's the same."
"If I have either," Tony whispered. "And I know my reactions aren't the same. My thoughts aren't the same."
"Aren't they?" Steve asked, laying a hand on Tony's thigh and running his fingers lightly back and forth over the inner curve of it.
Tony shuddered and licked his lips. "No, Steve, they aren't. Because I'm not thinking about pinning you down and fucking you right now. I'm thinking about sinking my fangs into your throat."
Steve blinked, but he wasn't entirely surprised, and he always had been good at changing tactics midstream. He tightened his grip around Tony's thigh, hard enough that it would have given Tony bruises once. "What about me pinning you down and using my teeth?" he asked, letting his voice go deep.
A strange, sharp sound emerged from Tony's throat. His eyes were wide, his body completely still for a moment, still in a way that a man whose heart beat and lungs worked couldn't be. Instinct told Steve that it was the calm before the storm, so he quickly leaned in, not to kiss, but to sink his teeth into Tony's throat.
Tony shouted, his whole body bucking against Steve. He was almost strong enough for the involuntary motion to throw Steve off of him, now, but Steve was ready for him, and he still had the weight advantage. He leaned and Tony gave way beneath him and they sprawled back across the bed, Tony pinned awkwardly beneath Steve. He struggled, but only half-heartedly, because he didn't shift Steve an inch. Steve felt a surge of strangely mingled relief and desire when he felt the hard, aroused length of Tony press against him as they fought, redoubling his resolve to hang on. At last Tony let out a low, breathy sound, and went limp.
Steve didn't release the bite until Tony had been relaxed for several long moments. When he pulled back, Tony stared at him, then slowly lifted one hand to brush his fingers over Steve's lips.
"So maybe this isn't going to work quite the way I imagined it," Steve said. "That doesn't mean we can't make it work."
Tony threw back his head and laughed and laughed until there were tears in his eyes.