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A low whimper comes from the man trapped between Sylvain’s body and the wall, and Sylvain smirks. He rolls his hips, crushing the length of his erection against Professor Byleth’s firm ass, continuing to nip and suck at the man’s neck.
“I knew you’d give in eventually,” Sylvain purrs darkly, “Professor.”
It’s taken ten moons of flirting and ramping up the sexual tension, but Sylvain’s not lying, he had known the Professor would give in eventually.
They’re soulmates, after all. There’s only so long anyone can resist the intrinsic pull of the bond, the desire to get close to their soul’s intended, no matter how strong they are inside.
Sylvain’s gone through a lot of complex feelings in regard to his soulmate in the last ten moons. Been a bit of an ass, making it look as if he’s taking random girls to bed in attempts to make Byleth jealous. Been even more of one, vaguely threatening to kill his soulmate for the privilege of being born with a Crest without knowing the torment of the expectations that privilege comes with for everyone else.
Through it all, though, Sylvain has known they’d end up here. All his life, he’s held onto the fragile hope that he’d be lucky enough to find his soulmate, the one person bound to love him for him. Not his Crest, not his nobility, not his money, but him.
He’d promised himself, in his darkest moments, that he would return that love tenfold. That he would devote himself to whoever they turned out to be entirely; treasure them.
All of Sylvain's shitty behaviour can be explained — but not excused — by how much pain Byleth's initial refusal to acknowledge the bond had caused him.
“I’m a teacher at your school, Sylvain. We can’t have any kind of relationship, not while you’re a student here. I’m sorry, but it’s going to have to wait.”
Sylvain never claimed not to be a true noble in some ways, as much as he despises the ideals of nobility, and one of those ways is struggling with not getting what he wants.
He had not taken that rejection, temporary as it was promised to be, well.
But now, here, curled around the strong lines of Byleth's body, Sylvain feels content. The divine string tying them together has finally been wound tight enough that neither of them can pull away.
Not after Byleth had almost been taken from Sylvain for good by that forbidden spell; a reminder of how precious whatever time they have together is, of how irrelevant their respective positions within the Academy truly are.
“Sylvain,” Byleth tries weakly, trailing off into a moan when his hard-on is cupped and squeezed by Sylvain's hand. “S–Sylv— haahhh,” he gasps, arching his back when Sylvain rolls his palm over Byleth’s erection and bites the juncture of Byleth’s neck and shoulder. His ass, the muscle toned and firm, rubs against Sylvain's cock and makes Sylvain breathe out shakily, rocking his hips forward towards the source of pleasure.
“How long have you wanted this, huh? Has it been as hard for you as it has been for me, not giving in to the pull?” He kisses his way up Byleth’s neck before licking just behind Byleth's ear teasingly. “Because it's been torture for me,” he continues, grinding fully against Byleth’s ass now, breath coming in harsher pants, “I’ve practically jerked myself raw, thinking about finally getting you underneath me like this, Professor.”
Byleth pushes the solid line of his cock into Sylvain's hand harder. “I d– I don’t– ah!” He cuts himself off with a gasp, his nails digging into the wooden wall Sylvain has him pressed against.
Sylvain laughs lowly. “Don’t try and lie to me, dearest soulmate,” he murmurs, stroking his hand up and down Byleth's clothed dick. “I can feel how badly you want me, how hard you are for me. So tell me, Professor, how long have you wanted this?”
“Since we first met,” Byleth admits in a whisper as if he’s embarrassed, “but then Rhea made me a professor, and even with the bond, I didn’t think— nnghh— it was appropriate, so I pushed it down.”
Clicking his tongue in a disappointed tut, Sylvain reaches for Byleth’s face with his other hand and turns his face so that Byleth’s lips are halfway visible. Then, Sylvain kisses him. Roughly, possessively.
There’s something in his chest, something primal, wrapped in their bond, and it wants nothing but to claim Byleth as Sylvain's own — just like Sylvain himself.
Byleth melts into it, squirming as he alternates between trying to rub against Sylvain's hand and his cock. The animalistic thing inside Sylvain preens, proud to have reduced his strong, divine soulmate to such a needy wreck with just a few touches.
“Tell me,” Sylvain says silkily, his lips brushing against Byleth’s as he speaks, “did you touch yourself, thinking about me? Even when you were pretending you weren’t this desperate to be touched by me, hm?”
Byleth’s breath hitches audibly before he answers. “Yes.” Just the one, damning word is enough to make Sylvain’s cock twitch, leaking pre-come into his pants.
Sylvain keeps questioning, chasing the pride and arousal that comes from his soulmate’s answers to things like ‘how often’ and ‘did you just wank, or did you finger yourself thinking about my cock’ as he continues to rut against Byleth’s ass like he's nothing but the beast inside his chest, wrapped in their bond and feral for Byleth and Byleth alone.
But then he gets to ‘did you let anyone else touch you’ and something about the way Byleth stiffens tweaks at Sylvain's instincts.
“Has anyone touched you, dearest soulmate? Has anyone else ever known the sight of your body, stripped naked and wanting? The touch of your bare skin, the sounds you make when you come?” He asks, voice like velvet.
Byleth hiccups a moan at the accompanying, firm stroke of Sylvain’s hand around the outline of his cock and shakes his head. “No. I’ve never— I’ve never been with anyone else.”
Sylvain all but growls in approval before spinning Byleth around and hoisting him up, curling his hands around the backs of Byleth’s thighs to hold him in place.
“Your place or mine, gorgeous?” He teases, delighting in the delicate flush that suffuses Byleth's high cheekbones at the pet name.
He might be little more than an animal right now, but he’s not letting his soulmate, his precious Byleth, get fucked for the first time against a wall outside the student dormitories. Byleth deserves better than that.
Sylvain stares down at Byleth as he writhes on three of Sylvain’s fingers, his eyes dark with desire at the sight of his soulmate in such a state of undoing.
There are literal tears of pleasure clinging to Byleth’s eyelashes like morning dew, and there’s a pink blush spanning the distance from his cheeks to his chest.
“That’s it, sweetheart,” Sylvain coos, “just like that, just let yourself feel good.”
Byleth heaves a breath, the exhalation trembling out of him. “It’s— it’s so much,” he gasps, looking at Sylvain with eyes that don't seem to be able to fully focus. “So good, so much, f–fuck!”
Sylvain groans when Byleth clenches around his fingers and grinds down onto them, hips moving seemingly on their own as his soulmate’s lashes flutter and a litany of moans spill from him.
It’s so arousing that Sylvain can’t resist the urge to touch his own cock, pumping it lightly so that the combination of touch and sight doesn't send him over the edge before he’s sheathed in Byleth's body.
“Sylvain, I need– I need–” Byleth stammers, whimpering too much to get a full sentence out, but it's okay, because Sylvain knows.
Their bond is pulled taut between them, the urge to get close stronger than ever before, and Byleth’s clearly had his fill of the agony it’s been to resist it from the way his hands fist in the bedsheets, knuckles white, and the noises spilling from him turn more desperate with every iteration.
“I’ve got you,” Sylvain reassures, his voice dark enough with desire to make Byleth's leaking cock twitch. “I know what you need, Professor. Do you want me to give it to you?”
“Yes,” Byleth whimpers, his hole fluttering around Sylvain’s fingers as they withdraw. Maybe it’s a little cruel of Sylvain to take advantage of how clearly overwhelmed his soulmate is, but he thinks he’s earned the right to tease a little after being made to wait for so long.
It’s not as if he’s even considering not fucking Byleth until he can’t remember his own name. His dear little soulmate will get what he needs, but… In a minute.
“Oh, really,” Sylvain purrs, gripping his erection and guiding it to Byleth's entrance, rubbing the damp head of it around Byleth’s rim. Byleth’s body seizes, back bowing as he tries to push his hips down onto Sylvain, but Sylvain is prepared for this and tips his pelvis backwards to keep the distance the same. “You’re sure you want this? Because you spent an awfully long time avoiding it, Professor.”
“I’m sure,” Byleth croaks, his stomach muscles rippling as he continues to mindlessly squirm for Sylvain's dick. The primal thing in Sylvain’s chest likes this, likes this view of what’s theirs so debauched and wanting for them.
“I’m not sure I believe you,” Sylvain whispers as he pushes into Byleth’s stretched heat, not even immersing the entirety of his tip inside it, taunting. “Why don’t you convince me, hm?”
Byleth’s eyes are squeezed shut, silent tears leaking from beneath his eyelashes as his mouth opens and closes helplessly.
Taking pity on the beautiful man beneath him, Sylvain instructs him further. “Beg me, Professor. Beg for the thing you’ve been denying yourself, denying both of us, for so long.” He pushes in a little further, encasing his whole cockhead in Byleth's hole, and groans gutturally at the stimulation to such a sensitive point.
Neither Sylvain nor his animal is disappointed by the results their final demand gets them. Byleth whines, high-pitched and pleading, as he speaks and speaks and speaks. Tells Sylvain he wants to feel Sylvain's cock stretching him, wants to feel them joined together desperately. Tells him that he's never felt so good in his life and wants more, wants everything Sylvain will give him.
That he's never wanted before meeting Sylvain and then it was hard to do anything but want, so will his soulmate please, please, fuck him?
Sylvain obliges with glee.
Sitting on his heels, he spreads Byleth's pretty, pale thighs further and wraps his arms underneath them. He hauls Byleth towards him, pulling his soulmate up the incline of his folded legs and onto his cock in one, smooth motion.
The noise Byleth lets out can only be described as a sob of relief. If he was less consumed by the feeling of their bond finally completing, Sylvain would be murmuring praise over how well Byleth is taking him — but his nerve endings are blazing, a fire in his chest where the bond and Sylvain’s animal desires sit, and all he can do is moan loudly as he fucks into Byleth over and over again.
He works them both to a steady rhythm, hips pumping his length into Byleth’s clenching hole in hard, deep strokes that have Byleth practically screaming Sylvain's name.
There’s no way at least a few of his neighbours haven't been woken up by the racket they're making or recognised the voice of the man Sylvain is fucking into oblivion, but Sylvain couldn’t care less about either of those things.
He wants everyone to know that Byleth is his. His soulmate, his to make scream with primal satisfaction, all his.
“Fuck,” Sylvain grits out, feeling the tingle of his climax glittering at the base of his spine. He wants to see Byleth come on his cock before he spends himself, needs to.
To that end, he grabs Byleth’s hips and shifts them until he knows he’s hitting his soulmate’s prostate from the loud, wordless cry of pleasure Byleth lets out, his cock jumping against his stomach as pre-come pools beneath it from the steady drip.
“By, shit, I’m gonna come,” he grunts, trying to decide the best way to speed Byleth’s own climax along before he settles on, “touch yourself for me, gorgeous. Let me see you— fuck— let me see you play with that pretty cock of yours until you come.”
Byleth whimpers brokenly as his velvety walls clamp down on Sylvain’s girth, doing as he's told and wrapping his fist around himself before stroking. His back arches, hips pushing his length into his own hand as his muscles tighten even further around Sylvain.
“Syl, Syl, Syl, I’m— shit!— coming, I’m coming, I’m gonna—haaahhhh," his soulmate breaks off, spurting jets of white fluid over his stomach and chest as his hole practically strangles Sylvain’s cock.
Sylvain’s orgasm is all but ripped from his body, the sounds coming from him more beast than man as he slams his hips into Byleth’s ass one last time and then stills. His hard-on jerks against the tight hold of Byleth's muscles, unloading spurt after spurt of his satisfaction into his soulmate as a shudder wracks his body.
In the background of all the overwhelming, delightful sensations Sylvian is feeling, is the warm contentment of a completed bond, humming away in his chest and granting him soul-deep peace. They are connected, irreversibly and irrevocably.
Later, Sylvain will ask Byleth how the hell he lasted so long during his first time, and Byleth will blush as he admits that he actually came for the first time outside, against the wall. He had just forced himself to bite his tongue knowing they could be discovered at any moment, he will tell Sylvain, and Sylvain’s animal, docile now, thanks to their bond, will purr in gratification at the information.
But for now, Sylvain focuses on blinking his vision back to normality from the brilliant white light that has overtaken it as his body crashes back down to earth, where his soul is tethered to Byleth’s, exactly where he belongs.