She was getting used to the marks he left. They splotched here and there; the five dots of his metallic fingerpads where they'd dug into her hip, the scrape of an automail leg when muscles had contracted in a moment of ecstatic release.
It's why she got the handcuffs.
It was a novel approach to controlling Edward. He wanted to be wild and free, burn fast and fuck hard. Teenage, male, and over eager, he lacked the knowledge of timing or foreplay. It's not to say he wasn't learning, but he was still careless. Had he been anyone other then the Fullmetal Alchemist, it probably wouldn't have mattered. It probably would have been normal.
The Fullmetal Alchemist, however, was not normal. He was 'special' in so many ways—and he had two heavy limbs, with sharp edges that had to be beveled down, curved and smooth, so they didn't catch on skin. He had a hand that could crush delicate flesh and bone with the brain's impulse that told electronic nerves 'spasm and clench' at the height of ecstasy. They felt nothing but they were still wired to behave like normal limbs, to catch and respond to the impulses fired out by the brain.
The brain sent so many messages during sex; so many messy, insane impulses; shudder, clench, buck, thrust, breathe. All his limbs responded naturally, fluidly, normally. It was a testament to the workmanship of his lover and mechanic, the girl who bore the Rockbell name that was branded to each of the pieces of machinery that protected him on a daily basis and scraped or blackened her whenever they got out of control like teenagers do.
Winry was tired of wearing the bruises.
He'd looked at her in shock, almost frightened. Stretched out under her hands, she'd smoothed them up his arms, and then dipped beneath the pillow to the cuffs she'd hidden there. It was not what he expected of the mechanic; certainly, she topped as often as he did, but it was never about power or control. Winry never needed a reminder of who was in control; in the bedroom, she was Goddess and her wrath was to be reckoned with. Edward was merely consort, and loved it. Not that he didn't get his chances to turn the table...
The handcuffs, however, changed the dynamic entirely. She was God now, with the power to bless or damn him in their bed, to hurt or harm if she so chose—to leave him with no control.
His face contorted. She smiled sweetly. He trembled. She caressed.
Leaning down, she left her own mark on his neck, sucking sharply at his pulse. Feeling him squirm and groan, she reached back; his arousal was still obvious, easily grasped, and he forgot about handcuffs and thought about touch the more she explored his frame without him to impede her. Shifting to take him to the hilt, Winry began to ride out the passion and sudden anxiety she'd engineered. She kept high on his hips, away from automail legs and arms, watching his fingers splay and curl, unable to reach out, to touch her, hold on to her, control her.
She had it all in that moment. He began to move his hips with hers; arching but restrained. Edward was like on a dog on a too-short leash, so close to the bone but unable to taste it. She watched his stretched out body move; muscles dancing across his chest, up his one good arm, through his neck as he tossed his head back and worked beneath her. She could feel when feet braced and and knew toes splayed with the oncoming rush of climax.
He came hard, and she followed not long after. She lay atop him for a moment, listening to the rapid tattoo of his heart against his ribs. He was satisfied, boneless, and probably sore from straining against the cuffs.
The keys were found, the restraints unlocked. They continued to lay together in silence, sweaty and satiated, his arms loosely around her now, the automail one carefully laid over his own flesh and blood limb.
"... you can use those whenever you want. Just—fuckin' warn me next time."
"Where would the fun in that be?"
He laughed breathlessly, and she knew he couldn't disagree.