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in fidelity

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Keith had never considered himself to be a bad person.

He had been troubled when he was younger, it was true, but his violent tendencies had never been born out of the innate need to cause another person harm for no reason other than to hurt them. He threw punches first and asked questions later because he didn’t know how else to direct his feelings. And really, he didn’t want to hurt anyone; he only threw the punches because they hurt him first.

Maybe that’s why he latched onto Shiro so easily when they first met, during a time when everyone assumed that Keith was simply a bad seed with no hope of redemption. Shiro was so good, so honorable, the kind of person Keith had always wanted to be growing up. And thanks to Shiro, Keith had finally managed to see all of the potential within himself, and had even managed to become that good person he had seen hidden in himself when no one else had bothered to look that far.

Keith can’t seem to focus on good or bad right now, though. Not when Shiro’s ring is forgotten on the bedside table. Not when Shiro is gripping his hip so hard Keith will have bruises the next day, not when Shiro’s prosthetic hand is pressing warm and firm into Keith’s shoulders to keep him pinned down, and especially not when Shiro fucks so deep into him Keith swears he can feel it in the back of his throat.

It should feel wrong. It should make them bad people. The great, honorable Shiro, an adulterer. But they aren’t doing it to hurt anyone, Keith tells himself. Not purposefully, anyway. They were doing it because they loved each other. They had only figured it out a little bit too late, and Shiro had run off and gotten himself married in the meantime.

It wasn’t Shiro’s fault, though. How else was he supposed to feel when Keith called him a brother? What was he supposed to do when he got the idea in his head that he would only hold Keith back from all of his potential? Keith couldn’t blame him for trying to find happiness elsewhere, not when it took him just as long to confess his own feelings, too.

And really, it was Shiro’s inherent goodness that kept them in this situation. His kindness that’s kept him from ending his marriage and hurting the man he has called his husband for over two years now. Shiro never wants to be the cause of anyone’s pain.

But then, Shiro is also only a man, and for as much goodness is in his heart, there is equally as much desire. And Keith loves Shiro, and would do anything for Shiro, would do anything to make Shiro happy. Shiro deserves it, after all he’s been through. He deserves to have what he wants, even if it meant doing something wrong.

And if letting Shiro use Keith’s body like he owns it will make Shiro happy, well… That’s just mutually beneficial.

“Fuck, Keith,” Shiro groans as he bends over Keith’s back and grinds in. Keith’s eyes roll back and he can’t help the open-mouthed smile, not when he knows it’s his body that’s making Shiro like this.

And Keith likes Shiro like this. He likes giving Shiro the opportunity to be selfish, to just take and take and take until he’s satisfied. He likes it even more because Shiro is still Shiro, and he’ll always make sure he gives as much as he takes.

Shiro stills, and Keith whines and wiggles back, pushing himself up onto his hands for leverage. He begins rolling his hips, fucking himself on Shiro’s cock and fuck, Shiro is big. It doesn’t seem to matter how many times they do this; Keith will never be used to the burning stretch and the aching fullness that leaves him feeling it for days afterwards. It almost hurts, but it’s so good, the best kind of pain that leaves Keith begging and insatiable.

Keith had meant to coax Shiro into fucking him again, but he forgets all about that as he grinds his hips back. Keith shoves his hips back as far as he can—he wants it deeper, he wants everything Shiro can give him and then a little more. He hangs his head and moans as he moves his hips in little circles. He could come untouched like this.

Except Shiro grabs Keith’s hips with both hands and stills the movements. Fuck, his hands are big, too. Shiro is just… big, and Keith is in love with how much of his narrow hips Shiro can cover with his palms. Even his human hand is enough to span across all of Keith’s chest and hold him there. Shiro could do anything to Keith, anything he wanted, and the thought always manages to make Keith dizzy.

Shiro slips his hands back over the curve of Keith’s ass, pressed firmly against his hips, and spreads Keith so he can look at where he’s splitting Keith open. Keith’s entire body shudders and he turns to look at Shiro as best he can from over his shoulder. Shiro is smiling, looking down in amazement or awe.

“Look at how good you are for me, baby,” Shiro says lowly as he drags the tip of his finger over Keith’s rim, stretched to its limit around Shiro’s cock.

Keith mouth falls open and he can’t even form words. “Hah…” He arches his back and tries to push back again, but Shiro’s grip is still firm and holds him still.

Shiro pulls out and thrusts back in, and Keith’s body lurches forward. “Nng, fuck, Shiro!” He feels the blanket tear under his fingers, under the claws that are growing from his nails. His vision gets hazy around the edges. His mouth hangs open and he drools obscenely but it’s just so good, so, so good. He feels his cock drip when Shiro reaches forward and shoves two fingers disgracefully into his mouth, his knuckle scratching against a sharpened fang and smearing a drop of blood over Keith’s tongue.

Keith’s arms are shaking but he keeps himself up, he even arches his back the way Shiro likes. That makes Shiro groan low and move his hand back from Keith’s lips to grip into the meat of Keith’s hips even harder. Keith groans, lifts his head, and—


There is Curtis.

He stands in the doorway, watching, expressionless, as his own husband has sex with Keith. On their bed. Shiro hasn’t noticed him—he wouldn’t still be fucking into Keith like it’s that or death if he had. Keith just stares back, not knowing what to do or what to say. His body moves forward and back with every thrust but he just keeps on looking at Curtis, maintaining eye contact.

He can’t take it anymore. He opens his mouth to get Shiro’s attention, even begins to reach back so he can push Shiro off of him.

Anything he was about to say dies in his throat and turns into a hungry, whiny moan as Shiro thrusts into his prostate. Keith’s face screws up in pleasure and his eyes roll back. That finally breaks the eye contact. It’s like Curtis isn’t even there anymore—rather, it’s like Keith doesn’t care that he’s there, watching as Shiro fucks the life out of him. Not when Shiro does it so well.

“Oh, fuck, fuck! Right there right there right—Shiro!

Curtis turns and leaves.

Maybe Keith isn’t as good of a person as he once thought.

“Fuck, Keith, I’m coming, I’m—“

That gets Keith’s mind off of his dilemma quickly. Shiro’s voice drives Keith insane, low and hoarse and so tight as he tries to hold himself back. One day, Keith is going to make Shiro scream.

For now though, Keith just nods frantically. “Inside, inside me Shiro, please!

Somehow, through his pleasure haze, Keith manages to hear the front door close.

Keith’s orgasm hits him suddenly and hard. He yells sharply and lets his shoulders fall to the bed so he can bury his face into the blanket as he growls and trembles and stains the bedding. Shiro reaches under him and grabs his cock and milks Keith for every drop, until all Keith can do is lay pliant under Shiro with tears clinging to his eyelashes. He moans and whimpers as Shiro fucks his ass and plays with his cock, overstimulated and feeling like he’s left his body at the same time.

Shiro thrusts into Keith three more times and then buries himself balls deep with low moan that morphs into a needy whine as he comes inside of Keith. Keith smiles into the blanket as Shiro fills him, moans like he’s making a sex tape when Shiro gives one last shallow thrust. Keith can feel a drop of Shiro’s come leak out and run down his inner thigh, and that makes him shudder.

Keith isn’t exactly sure how long it takes for Shiro to finally let out a shaking breath and pull out of him. A hand on Keith’s shoulder has him rolling onto his back. “Come here,” Shiro says, his voice all soft. “I want to see you.”

Shiro looks down at Keith with a smile that makes Keith’s heart light up. Nothing is more beautiful than that, Keith thinks. He should tell Shiro that. Instead of speaking, he pulls Shiro down for a kiss, sweet and soft compared to what they just shared together. Shiro kisses down Keith’s neck and chest, his flesh hand running down the length of Keith’s body.

“Oh…” Shiro sounds contemplative and smug. “We made a mess.”

Two fingers push into Keith. Keith chokes on a moan and his breath hitches as Shiro presses in deeper and curls his fingers. Keith arches his long body up, tilts his head back so his hair spills against the blanket.

“I’m going to have to clean you up,” Shiro says, low and dark as his fingers slip out of Keith again. Keith blinks and lowers his body back down to the bed so he can look up at Shiro properly, smiling and excited for what’s to come. Shiro catches something though, and he looks forward, towards the door. “Hmm? What are those?”

Keith frowns and lifts himself onto one elbow so he can see for himself. Papers, forgotten and scattered on the floor of the doorway. Something falls into the pit of Keith’s stomach. Curtis must have dropped them.

Shiro moves to stand, but Keith grabs his arm to stop him. Shiro looks back at Keith, blinks those big eyes that are still so full of youth and wonder. Keith swallows and pulls Shiro back close to him so he can kiss him again.

“I love you, Shiro,” Keith tells him. The words come easily to him. They always have.

“I love you too, Keith.” Shiro smiles, but he looks confused and very suspicious, like he knows Keith is going to follow it up with something else. Like there’s a bomb waiting to be dropped.

Keith sighs. Shiro was and always will be very perceptive.

“Shiro, you need to know…”

Keith wants to be a good person.

For Shiro, he wants to be everything. For that, he’ll let himself be bad.