A/N: This fic was written for the fic-on-demand LJ community for a request for an Ed/Psiren lemon (so yeah, there's not a whole lot of plot in this story). This fic springs from episode 10 of the anime, which I believe is the only episode Psiren ever appeared in, and there are a handful of references to that episode mixed into the story.
Psiren sighed, pulling tightly at the restraints on her wrists. She had not expected such passion from the boy who had blushed and stammered the last time he had an opportunity to feel her breasts. Now he caressed them with great delight as he slowly explored the wonders of her body. A few years had changed so much.

This connection between them had started the very first time they fought, when he had landed on top of her, his hand unintentionally cupping the swell of her bosom. She had seen him take that step towards manhood, his eyes filling with lust for a brief moment as he looked upon her as a woman rather than as an opponent. She couldn't help but use that to her advantage.

At first, it had just been a game. She would draw down her zipper much lower than necessary to reveal her alchemical tattoo, she would wink at him even in the midst of battle, she would play on his heartstrings and make him believe she was far nobler than any theif could be. But then she had kissed him, and that had changed everything.

She knew it was a foolish thing to do. Despite having achieved the rank of state alchemist, he had been so young, but then again, she always had been impetuous, and he had saved her from the trap the police had set for her. So she had offered to thank him as a grown woman, bending down so that her breasts were intentionally at his eye level and asking him if there was anything she could do for him. It was a blatant offer. And it was a testament to his naiveté that he had completely missed it and begun rambling about the philosopher's stone.

Still, she had wanted to leave him with something, so when he had finished talking, rather than answer his questions, she leaned forward and gave him a lingering kiss. Then, before he could formulate a response, she had disappeared into the night.

Of course, later that week he had still delivered her like a trophy to the local law enforcement, but she had probably deserved that for all the lies she told him. To mend things, she offered up the small bit of knowledge she possessed regarding his precious philosopher's stone, and he had disappeared, leaving her trussed up in handcuffs at the mercy of the police. She thought that had been the end of it, but she was wrong.

It took him several years to work his way back to the City of Water, and when she had encountered him roaming the streets at night, she could tell he was indeed an adult now, rather than a boy playing at being man.

Physically, of course, he had grown. He would never be a tall man, but it would no longer be fair to call him short. His shoulders had broadened and his hair was even longer, but these changes were all to be expected. The most striking difference was the absence of his automail. In its place was what appeared to be a healthy, living limb. She assumed this meant he had been successful in his quest. The lack of guilt in his eyes (and the absence of his hulking, metal shadow) certainly seemed to confirm that suspicion.

She did not know if he had sought her out, or if the meeting was purely coincidental, but when their eyes met, the tiny embers of passion that had always existed between them suddenly ignited into a roaring flame, which only grew more intense as they drew nearer to one another. By the time they were standing face to face, they were both breathing heavily, as if they had run to greet one another rather than approaching at a snail's pace. There was no idle talk of what each of them had done in the past few years or how life was treating them. He merely said "I am a grown man now," before pulling her into his arms and kissing her soundly.

Neither of them spoke a word after that. She just took his hand and led him back to her tiny apartment. At first, there had been a frenzy of flying clothing as each of them desperately tried to reach bare skin under all the layers of cloth, but once they were both nude, the pace slowed to a tantalizing crawl.

She was fascinated by his hair, running her fingers through it over and over again as she kissed him. It was so long that even when her kisses began to trail down his chest towards the aching member between his legs, she could still clutch it at the small of his back. She used his hair to pull his head back as she took him into her mouth, making his whole body arch into her touch as she curled her tongue around his length and pulled him in and out of her mouth in long, steady strokes.

When it became too much for him, Ed pulled away from her with an unsteady gasp before turning the tables and pinning her underneath him. For a moment, he merely laid on top of her, his forehead resting against her shoulder as he tried to regain control of his raging hormones. After he had calmed himself, a wicked grin spread across his face. Without warning, he reached to his side and transmuted part of her bed frame into a pair of handcuffs, using them to secure her hands to the headboard.

Once he was satisfied that she was firmly bound, Ed began his own exploration, his hands mapping the curves of her body, and his mouth following soon after. When he reached the juncture between her legs, she opened them willingly for him, and he eagerly began lapping at her juices. He waited until she too was near climax before he crawled back up her body and entered her slowly, watching her eyes to make sure that he was not hurting her in any way. His eyes never once left hers as he moved inside of her, not until they were both shuddering in release and her body had milked him of all he had to give. Then, not bothering to undo her restraints, he pillowed his head against her breasts as they both drifted off into a satisfied slumber.

When Psiren awoke, Ed was gone…but not without a trace. Next to the bed was a bouquet of flowers and a note bearing his current address as if to say "until we meet again" rather than "goodbye."

That did not change the fact that the bastard had not bothered to free her from the restraints that bound her wrists to the headboard. True, it was a simple matter for her to use her own alchemical skills to free herself, but that was not the point. This was the second time he had disappeared, leaving her behind bound in handcuffs.

Next time she would be sure to return the favor.