A/N: This is actually my first time ever writing and/or posting something like this so I hope I've done it justice. I've always kinda headcanoned that Roy and Riza had basically been sleeping together for years by the time the events of the show start (most people probably do), and then I suddenly felt the need to write this. I got the idea from that moment where Riza tricks Envy by saying that Roy calls her by her first name when they're alone. Random fact: I also listened to "Pyro" by Kings of Leon on repeat while I was writing, purely coincidental, but it kinda works for Roy? Anyway, I hope you like it and let me know what you think.

"Riza . . ."

She didn't hear it the first time he said it. Her legs wrapped tighter around him, pulling him deeper inside. His pace quickened and she easily met his rhythm. Even though they'd only been working together for just under a year, they'd developed quite an efficient partnership from the very beginning. So it had come as no real surprise to them when they discovered that they were as well-matched as lovers as they were at everything else they did together.

Their affair had started just six months after the war ended. Roy had quickly been promoted after his accomplished work in Ishval, and he'd specifically requested that Riza be assigned to him as his subordinate. He felt responsible for her, and he wanted her by his side. Surprisingly his request had been approved, and once they were reunited the pair seemed well-suited together, just not only in the way Roy had originally intended.

It had started out as a source of comfort, for some sense of relief. They were simply two broken people with tired eyes and weary minds, coming together to feel good again, if only for a little while. Now five months after it all started, they still insisted that's all it was and ever would be.

"Oh, Riza . . ." he moaned into her neck again.

That time she heard it. The use of her given name surprised her and she stilled. Her voice came out calm yet forceful. "Don't."

He stopped and eased back while still staying inside her. Raising his head to see her face, he asked breathlessly, "Is something wrong?"

"You called me Riza."

Roy panicked for the briefest moment, thinking he'd called her by the wrong name. How unfortunate that would be! But no, he knew he hadn't gotten it wrong. He hadn't been with anyone else but her for a long time. Chuckling, he asked, "Well, that is your name, right?"

"Not to you it isn't."

He frowned and shifted onto his forearms. It seemed he had displeased her somehow and that they weren't going to be getting right back into things. "What is that supposed to mean?"

"Don't say my name."

His frown deepened. That's what this was all about? The use of her name? Well, it wouldn't be the first time his mouth had gotten him into trouble in the bedroom. Sometimes Roy just couldn't help the things he said in the throes of passion. He was an especially loud lover, and he often said things to her in those moments that he'd never dream of saying anywhere else. There were times he found himself saying stuff like, "You're so goddamn beautiful," along with other equally mushy things, only to leave him somewhat embarrassed when he came down from his orgasm.

And just last month, after she'd taken him into her mouth, he'd yelled out quite forcefully, "Oh god I love you!" After he came, he couldn't even look her in the eye. Red-faced and stuttering, he said, "S-sorry, I didn't mean to – I didn't mean that." He laughed nervously. "Heat of the moment, you know?"

She'd sat back on her heels, her gaze even and nonjudgmental. "Of course, sir."

And after all of that, this was thing she decided to scold him over? He didn't understand it. "Why not?"

"If you start calling me Riza here, you might say it at work."

He chuckled again, slowly easing himself in deeper as he met her mouth with his. "You think something that simple could give us away?"

She shifted her hips to better take him in, her eyes steady on his. "You never know. One slip up is all it takes. Then this would be over."

"And we wouldn't want that."

Honestly, he thought she wasn't giving him nearly enough credit. They'd managed to keep the utmost professionalism at the command center so far, not giving anyone there even the slightest hint of their "romantic" involvement. They never touched each other inappropriately or sneaked off into empty rooms. Even the way they looked at each other was kept carefully under control. If he could do all of that, he could easily keep from calling her by her first name in front of others.

In the end, he felt this argument wasn't important enough to win, so he sighed and relented. "If you think it's best."

"I do." She kissed him then, long and heated. "Now come on, we aren't finished here."

Soon they found their rhythm again. They had each other twice that night and once again in the morning before he left her alone in her bed, the morning still gray and foggy as he made his way to his own apartment for a shower and a change of clothes before work. That was just the way it had to be if they wanted to keep this thing going.

And months later, when they'd long stopped defining their arrangement as strictly sexual, they were in her bed again. They lay there together, breathing heavily and their bodies slick with sweat. Roy laid his head on her chest, tucked just under her chin, and it rose and fell with her breath.

"I love you," he said, his voice a ragged whisper. And he meant it. Hell, he felt sure he'd meant it the first time he'd said it.

She knew he meant it too. Her eyes closed and she held him tight, one hand smoothing his damp hair. She let out a slow, even breath and her smile faltered. Riza didn't want to do it, but at least one of them had to be practical, and she knew it wouldn't be him.

"Don't say that either."

A/N: I only just learned it's Royai week on tumblr and today's theme is catalyst. Obviously I didn't write this with that in mind, but I guess if I'm reaching then this could be the catalyst for why they don't use their first names and ultimately gave Riza the idea to use that to trick Envy? Yeah, let's go with that. Thanks for reading.