Smut ahead. Not particularly explicit, but skip if it's not your thing.
After Tony and Bruce had done some scans and promptly removed the HYDRA arm, Bruce had sat down with Steve and gave him a thorough talk about the stress and damage the arm must've been putting Bucky through. What was worse, was that he'd clearly been dealing with it for so long, that the constant pain was probably 'normal' for him, given the fact that he never brought it up when the two scientists had originally quizzed him about his arm.
Tony had originally wanted to wait until he had a working prototype to replace it with, but after the scans, they decided it best to take it off and relieve that stress first. Bucky had refused the frankly comical-looking – in comparison to his HYDRA arm – standard prosthetic arm that Tony had pulled out. Bucky was clearly more than okay with the idea of Tony leaving him armless for good, despite how offended the man claimed to be.
It wasn't much of a treatment, but Bruce, via JARVIS, had ordered some massage oil delivered to their floor with some recommended videos on how it could help relieve the tension in Bucky's back, shoulders and neck. It would have turned into an argument, if Steve didn't firmly put his foot down about doing it.
That's how it became a near nightly ritual for Steve to spend a good hour massaging Bucky's back before bed. After the first few nights, Bucky had given up even trying to keep up a façade of complaining, clearly admitting just how much he actually enjoyed the sessions.
"Uhnn…" Bucky let out a particularly loud groan as Steve worked his knuckle deep into a knot, releasing the tension. His fingers, curled around the pillow, twitched as he buried his face deeper in to the soft pillow.
Large hands swept down his back, to the curve just before his hips, and kneaded expertly. Bucky's back shined with the warm oil, and then when Steve curled some fingers around his hips to tilt them further as he pressed his thumbs into the small of his back, Bucky shuddered around a moan.
"Buck," Steve almost whined in warning, glancing up to see a single eye peeking back at him from over the pillow. Steve's breath stuttered, and he splayed out his hand over the back of Bucky's waist as he maintained eye contact. Staring silently at each other, Steve rubbed his palms back up to the top of Bucky's shoulders, then slowly back down.
Instead of resuming his work at Bucky's hips, he slowly slid his hands around to the front of Bucky's waist, then halted teasingly at the hem of Bucky's sweats. He felt the hitch of breath in the body beneath him, before Bucky was surging up and around to grasp at Steve.
Steve braced himself, but was still surprised when Bucky crashed their lips together. Bucky tilted dangerously, still overcompensating for the missing arm, but Steve steadied him with his arms wound around his waist.
"Steve," Bucky breathed between their lips.
Squeezing at his hips, Steve pushed with the barest of force, and made sure to keep a hand cradled behind Bucky's head as they fell back onto the bed. Bucky's arm was still clutching tight to Steve's shoulders as Steve wormed a hand to slide into the front of Bucky's pants.
Bucky jolted at the touch of Steve's fingertips, then broke their kiss to glance down and slip his own hand into Steve's sweats. Steve captured his lips once more, hard and demanding, but as their hands stroked each other, their kiss devolved more into panting into each other's mouths.
With a sharp twist of his wrist, Steve wrung a high keen from Bucky's mouth, staring ravenously at the way Bucky's brows furrowed and his head tipped back. Steve leaned forward to lick up that bared throat, sucking a bruise into the skin there.
Bucky's hand tightened around Steve, receiving a grunt in return, and then Bucky thrust his hips up, knocking their hips together and drawing a hiss from both men at the sudden motion. Growling, Bucky withdrew his hand quickly to shove at Steve's pants, then wriggled out of his own.
Getting with the program, Steve let go of Bucky only for a second before wrapping his large hand around the both of them, resuming his pumping. At the press of their lengths, Bucky gasped and arched into the feeling, his now empty hand floundering.
Glancing at it, Steve let go again to grasp at Bucky's hand, then promptly wrapped them both onto their lengths, pumping mercilessly. He felt the full-body shudder running through Bucky, and pressed closer so that their fronts were plastered together; chest to feet.
Rutting his hips down leisurely, Steve nipped at the faint stubble on Bucky's chin then dragged his teeth over it. Bucky tipped his chin down, flexing a little so as to catch Steve's lips in a kiss. A few more pulls later, Bucky whimpered and tensed as he crested over the edge.
Steve pulled back to watch as Bucky went from a tense arch of his neck, eyes rolling up and slipping closed, and then all tension drain out of him as he dropped back limply onto the sheets. He kept stroking them, coaxing the last few drops of cum out of Bucky, until the man below began to squirm as hazy blue eyes blinked open.
Ducking down to shove his face in the crook of Bucky's neck, Steve breathed in the thick smell of Bucky there as his hips stuttered and he came, gritting his teeth and groaning. When he came back to himself a moment later, it was to Bucky running a gentle hand down his back.
He pulled back just enough to look at Bucky's serene expression, drinking in the contentedness in his face and relaxed body. "I love you," the words felt like they were pulled out of him without thought. He watched as Bucky blinked slowly, then as his eyes softened and his hand came up to cup Steve's face. Steve closed his eyes and leaned into the touch, thanking every God up there that this was real.
When a thumb brushed under his eye, he blinked open his own to the painful stab of emotion that coursed through him at the sight of the tiniest of smiles upon Bucky's lips. Steve felt like his heart would burst out of his chest with how much it grew when Bucky opened his lips to whisper, "I love you."