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The Back Door

Summary:

Their sex life isn’t dull, but Keith wants to try something new.

Notes:

I’ve been haunted by the thought of this particular scenario so here you all go.

(See the end of the work for more notes.)

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Their first time was incredible. 

They were both so fucking bad at it. In fact, at first it was less fucking and more the both of them so desperate that they just gave up on removing clothes. 

Keith gasped into Shiro’s mouth, grasping at what was left of his shirt, as if maybe he could pull him closer than he was. His legs were wrapped tight around his waist, tugging him into his thrusts against Keith. 

Shiro panted, fingers burying themselves in his hair, his cock rubbing against his cunt through multiple layers of pants. Which was both the worst and the best. 

The worst because he really wanted what he could feel was a thick, big cock inside him, and the best because this on its own felt so fucking good. 

“Shiro.” he whispered, biting lazily at his lip and parting from him to gasp for air. 

Shiro nosed his way down his neck, planting a knee in the mattress and rolling his hips down, slower, harder. 

Keith reached down and grasped his ass, something to hold onto as he started to come. 

Shiro grunted and moaned in his ear, Keith’s breath came with a wispy, shaky sigh, and then Shiro’s hips started to roll to a stop. 

Keith trembled, chuckling softly. 

He supposed all this tension between them had to give eventually. 

“Ah…umm…so…” 

Keith laughed again, and Shiro joined in, pushing Keith’s sweaty hair away from his eyes. 

“What’s this make us?” he wondered.

Keith looked up at him, a little unsure. 

“Dunno…what do you want it to be?” 

Shiro smiled, dopey and content. 

“Maybe something along the lines of boyfriends?” he suggested, and Keith smiled, turning his head with a blush. 

“That sounds nice.” he said. 

“Just nice?” 

Keith pouted, turning a frown Shiro’s way. 

Shiro just grinned, pulling away to roll onto his back beside him. 

“I’m teasing, baby.” he said, and Keith scoffed even as he smiled. He gave Shiro’s shoulder a shove, and then he groaned as he sat up. 

It wasn’t too messy for him. He had it better than Shiro at least, but still…

“Boyfriends then?” he asked. 

“Boyfriends.” Shiro confirmed. 

“Okay.” Keith said, and then he stood and pushed his pants down to the floor, stepping out of them and tugging his shirt over his head. 

Shiro watched in delight, cheeks rosy and a glint in his eye as he leisurely looked him over. 

Keith climbed back onto the bed and straddled his hips, sitting back with a toss of his head and running his hands down the length of Shiro’s abdomen. 

“Again.” he rasped, “Properly this time.” 

Shiro’s smile only widened, and Keith sighed when he gripped his hips, still-gloved hands dragging against bare skin. 

“You read my mind, baby.” 

Keith yelped when Shiro flipped them over, and then his breath stuttered off into another little sigh. Shiro’s tongue had delved between his legs, and Keith reached down to tug at his hair, head tossed back and his chest heaving as Shiro licked and sucked at his cunt. 

He didn’t bother to remove his gloves, Keith realized as a finger slipped inside him to the knuckle. 

“How’s that?” 

Keith lifted his head, and Shiro smiled from where he was resting against his thigh. 

“How’s what?” he wondered. 

Shiro’s smile vanished, and Keith bit his lip when his finger curled inside him. 

“That?” 

Keith chuckled, propping himself up on an elbow. 

“Well it’s okay…be nicer if you were moving.” 

Shiro blinked, “Ah…sorry I’ve never—“ 

“It’s okay.” Keith pet his hair idly, “I didn’t expect you to be very good at this.” 

Shiro barked a laugh, blushing as he rubbed his free hand over his face in a groan. 

“I haven’t even gotten started. That’s not fair.” 

“Yeah, but you just said you have no experience with trans men.” Keith said, tilting his head with a wry smile. 

Shiro stared. 

“I dug myself into that hole. Didn’t I?” 

“You kinda did.” Keith squinted at him fondly. 

Shiro sighed, and then he looked down at his finger, sliding a second one inside Keith. 

“Okay then.” 

Keith waited, and Shiro looked back up at him. 

“Tell me what to do?” 

Keith grinned. 


A year down the line meant a lot of growth for them. Not just sexually, but as a couple. 

Granted, sex was still a huge part of it, how could it not be? Years of tension and pining couldn’t allow anything less than…well…

Pretty much every fucking day. 

Keith closed his eyes, letting his head fall back as he rolled his hips against Shiro’s, sweat dripping down his back, thighs burning and trembling. 

They’d come a long way from their first time together. And while Shiro had fumbled a little, he was good at listening to Keith and his cues. He started to pick up on what felt good and what was bland pretty easily. 

Keith’s breath hitched, eyes wide as he glanced down at Shiro, who had that smug little grin on his face. 

“Yeah?” 

Keith chuckled huskily, and Shiro thrust up into him again. That angle was hard for him. He was big, and he usually slipped out when he was going shallow, but when he did hit that spot…

“Yeah.” he affirmed, eyes falling closed again and his jaw dropping. 

Shiro’s hands tightened at his hips, holding him in place while he planted his feet and repeatedly hit that spot. 

Keith couldn’t help a low moan, a bit of a growl, and Shiro redoubled his efforts, encouraged by it. 

Keith gasped and Shiro rubbed a thumb over his clit, drawing him closer to his orgasm, and Keith’s hands slipped where he had them planted on Shiro’s chest. Down to the mattress, and bent over like that only made it easier for Shiro to hit that spot. 

Keith’s exhale was a soft whine, barely there, but Shiro chuckled breathlessly all the same. 

“Love it when you moan, baby.” he whispered, and Keith blinked blearily down at him, smiling even as he blushed. 

He came only a few moments later. 

Shiro grunted when he clenched down over him, and Keith panted through it, breathy little noises every here and there, and then he collapsed against Shiro, groaning as his body jolted and quivered with pleasure. 

“That’s it, Keith.” Shiro said in his ear, nipping at the soft lobe and then pressing kisses to his shoulder as he rolled his cock into Keith. Slow and lazy as he chased his own orgasm. 

“Mmn.” Keith sighed when he felt him come, and Shiro moaned in his ear, a hand cupping his ass and squeezing as he pulsed inside him. 

“Fuck.” 

Keith giggled. 

“I needed that.” 

“Yeah.” 

Shiro sighed, petting through Keith’s hair and staring at him with a rather peculiar look in his eye. 

“What?” 

Shiro hummed, “I just…we’ve been together a long time.”

“Yeah?”

Shiro smiled, “I wanted to say that I’ve noticed you’re very quiet when he have sex, even when I can feel you coming. It’s interesting. 

Keith pursed his lips, “I’m quiet?” 

Shiro smiled, “Well, yeah. A little. Not that it’s bad. I just wonder if I’m not doing as good as I think I am.” 

Keith laughed breathlessly. 

“It’s definitely not that. I’m just not a very vocal person.” he said, pressing a kiss to Shiro’s jaw. 

“Ah…that makes me feel a little better.” 

“Just a little?” Keith wondered. 

“Mm.” 

“What could I do to make you feel all the way better?” Keith crawled up and sat on his belly, hands planted in the sheets beside his head. 

Shiro grinned, “Right now? Maybe take a nap with me.” he said. 

Keith huffed, and Shiro chuckled, rolling them over and resting his head on Keith’s belly. 

Keith obliged him his nap, though his words stuck in his head. 


“Keith, baby.” 

Keith stilled beneath him. 

“Are you…moaning on purpose?” 

Keith blushed, and Shiro craned his neck to see his face. 

“….no.” 

“Keith.” 

Keith sighed, “Maybe a little.” 

“Is this because of the other day?” 

Keith remained quiet. 

“You know I didn’t mean it as a bad thing, right? I was just checking in. Making sure I was doing good enough for you.” Shiro murmured in his ear. “You can be as loud or quiet as you want, baby.” 

Keith nodded. 

“Hey?” 

Keith looked at Shiro, and he smiled. 

Keith was a bit disappointed when he pulled out and laid down beside him, keeping eye contact. 

“Do you wanna try something new?” 

Keith frowned. 

“What do you mean?” 

“Like, I’m content with our sex life, but are you?” 

Keith considered that, “I’m content with you.” he said. 

Shiro smiled, “That’s not what I asked, baby. Relationships and sex aren’t always the same thing. Maybe you need something more than what we do. Maybe you need a little adventure in it?” 

Keith scoffed a laugh, “Adventure?” 

“Yeah.” 

Keith hummed, “Maybe. I’d have to think about it.” 

Shiro smiled, “I think I have my answer, then.” he said, leaning in to kiss Keith soundly, “Don’t be afraid to ask if you feel like you want something, okay?” 

Keith nodded. 


What do I want? 

Keith agonized over the question for a week. 

He didn’t really think much of it, he didn’t think there was much more to sex aside from what he and Shiro did. And now that Shiro had pointed out that he might be discontent, he was starting to think that maybe he was. 

Not that he disliked their sex life. He just…had some extra needs. 

So he went onto the galaxy-wide web. He watched porn, he read about different kinks or sexual adventures people went on, alien or otherwise. And there wasn’t much, but a few things did hit him right where he suspected he needed it. 

Discovery done, he did some research, and that done, he prepared himself that afternoon. A trip to the nearest store for lube and…a few extra things. And then at home he lay back in bed and stared at the plug. The most unfortunate thing about this particular desire was that he was a complete and utter virgin to it. 

And despite how nice it would have been, unlike his first time with Shiro, he didn’t think it such a good idea to take him right off the bat. 

He was…really fucking big. 

So Keith would work up to that, and he would start with this pathetic looking little plug about the size of one of Shiro’s fingers. 

Easy enough. 

He coated it in lube and reached down, clean and ready, legs spread, and took a deep breath, relaxing, and then pushing…

“Oh.” 


It took him a whole week to work his way up to the biggest plug, and he felt a little silly keeping it from Shiro, but he wanted to surprise him with it when he was ready. 

And now he was fairly certain he was. 

He hadn’t done much except stretch himself out, but what sensation he got from it had him gasping softly as he inserted and removed plugs. 

Something told him he was not going to regret this. 

Shiro got home weary, and Keith saw it as soon as he entered the room. 

“Hey baby.” Shiro sighed. 

“Hi…you okay?” 

“Tired.” Shiro smiled at him, “Think I’ll take a shower, maybe pass out early.” 

Keith wilted in mild disappointment, but he wouldn’t disrupt Shiro’s rest for sex. 

“Oh, okay.” he said, and Shiro looked at him funny, but he went and took a shower regardless. 

Keith sighed and flopped back on the bed, staring at the ceiling. He supposed the weekend would be better for something like this. Tomorrow, he could bring it up tomorrow. 

At least he was resolved to. 

Until Shiro flopped into bed with him and snuggled up to him, sighing as his hand rubbed over his hip. 

“What’s up, baby?” 

Keith tilted his head at him. 

“I can tell you’ve got something on your mind.” 

“It can wait.” 

“Hmm…can it?” 

Keith scoffed, “I mean. It’s just something I was thinking about...” 

“Oh? Sounds interesting, you know I’m all ears.” 

“Yeah,” Keith chuckled softly, “I know.” 

Shiro stroked his hand down Keith’s thigh, and then back up, teasingly brushing under his shorts, and then he stopped. 

“Did you want to…do something tonight?” he wondered, and Keith exhaled shakily when he thumbed pointedly where he had no underwear. And yes, that was in preparation for his plans tonight. But still—

“You’re tired.” 

“Yeah, maybe. But I also haven’t had dinner yet. I’m sure I can expend a little energy if you want to try something.” Shiro said with a sly grin. 

Keith smiled, “After dinner?” 

“And kill me with suspense?” Shiro sighed.

Keith giggled, “Maybe, unless you wanna do it now and eat later?” 

“I do.” Shiro said instantly, and Keith blushed. 

“Well…I was thinking about what you said. And I’m not…dissatisfied with our sex life.” he began, “But I think you’re right. Maybe I want to try a few things.” 

Shiro nodded. 

“Okay, baby. We can do that. What did you have in mind?” 

Keith bit his lip, and then he got up, standing up off the bed and pushing his shorts down his legs. 

Shiro watched in obvious enjoyment, though Keith heard his breath hitch when he spun around in a little circle. 

“What’s that?” 

Keith couldn’t help a smile as he turned to face him once more. 

“What’s what?” 

“Keith…lemme see.” Shiro sat up and reached for him, and Keith laughed as he spun him around and spread his cheeks with his thumbs. 

“Shit.” 

Keith looked over his shoulder, embarrassed, nervous, aroused… 

“Do you like it?” he wondered. 

“I love it.” Shiro gave the jeweled plug a testing tug, and Keith gasped. 

“Do you…want me to—“

“Fuck me.” Keith said, “In the ass.” 

Shiro exhaled a wheezy little laugh, “Okay.” 

He pulled Keith down into his lap. 

“That’s a big plug, baby.” he whispered in his ear. 

Keith blushed. 

“You’re big.” he retorted in a demure mumble. 

“Yeah? You ever done anal before?” 

Keith shook his head. 

“So you prepared for me?” 

Keith nodded. 

Shiro sighed, something husky and delighted, “I love you, Keith.” 

Keith scoffed again.

“I love you too…”

He yelped as Shiro spun the both of them around and pinned him to the bed. 

“Like this?” 

Keith looked over his shoulder, propping his hips up with a little wiggle that had Shiro delivering a playful swat to his butt. 

Keith laughed and nestled his head against his elbow, a hitching moan escaping him when Shiro slowly tugged the plug out of his ass. 

“Shit…it really is big. How did you even fit it?” 

“Lots of patience.” Keith said. “Lube in the top drawer.” 

Shiro moved to grab it, and he was back before Keith could even blink. 

“Excited?” 

“Very.” 

Keith chuckled, “Go easy on me.” 

Shiro spread his cheeks and drizzled a little lube onto him, and Keith gasped. 

“Cold.” 

“I’ll warm it up soon enough.” 

“Cheesy.” 

“Fact.” Shiro retorted, and Keith was about to reply, but Shiro’s slicked cock pressed against him and quickly slipped right inside and his eyes went wide. 

Oh shit. Oh fuck. 

If he thought the plugs were good. 

Keith struggled and clawed at the sheets as Shiro bottomed out, crying out a garbled, wailing moan. 

“Keith?” 

Keith gasped, inhaling deeply and shaking as he tried to wrangle two thoughts together. 

“Is it too much? Keith? It didn’t hurt, did it?” 

Keith shook his head, mewling and rocking back on his cock. 

“Keith? Words, baby.” 

“S’good.” Keith managed, “Please.” 

“Yeah?” 

Keith nodded frantically, and Shiro hesitated, but then he moved. A careful thrust had Keith wailing, and a hot flush overtaking him when he realized. 

It just…it was uncontrollable. He couldn’t help the noises escaping him as Shiro started to move consistently. 

“Sh-Shiro!” he cried out, muffled when Shiro turned his head and kissed him. 

“Fuck, Keith. You’re tight.” he rasped. 

Keith whined, a hand reaching back and grasping his ass to pull him in harder. 

“More.” he demanded, and Shiro was still only for a moment before he pressed Keith down by his shoulders and started fucking down into him in earnest. 

Keith screamed and writhed under him, tears of pleasure welling in his eyes. 

The plugs were nice, of course, but actually fucking…god. Keith hadn’t imagined it like this. Maybe it was a Galra thing, but this felt like their regular sex had been hyped up to twenty out of ten. 

Even better when Shiro pried two fingers into his cunt and curled them, thrusting in time with his hips. 

Keith’s ears rang with how much he was wailing and crying out, squealing and whining. He was certain this had all come about because Shiro thought he was a bit quiet. That would not be even a comment anymore, let alone an issue. 

“Nnng!” 

“Shh…feels good, hmm?” 

Keith whimpered as Shiro kissed his shoulder, nipping gently as his hips slapped into Keith’s. 

He couldn’t even answer. 

He seized up and tore a hole in the sheets, his voice gone from a scream to a breathy moan as he clenched and pulsed around Shiro. 

“Fuck!” 

Shiro halted and ground his cock inside him, mouthing at his jaw as Keith gasped and panted. 

“Shiro…” 

“How…how’re you doing, baby?” 

“More.” Keith rasped, looking over his shoulder, “Please just…keep going.” 

“Okay baby. Wanna turn over for me? I wanna kiss you.” 

Keith whined petulantly at the loss of his cock, but he rolled over regardless, spreading his legs and dragging Shiro back into his space desperately. 

“You like it, hm?” 

“Very.” Keith rasped, curling his hand in Shiro’s hair and tugging him down for a kiss, desperate and feral. He nipped at his lips, a moan breathed into his mouth when he fucked back into him. 

“Mm. I’m glad you like it, baby.” Shiro panted, “I like making you feel good.” 

Keith whimpered, his next cry muffled by Shiro’s lips. His every breath laced with a moan and a shout as Shiro rolled his hips. God, he was losing his mind. His nails raked down Shiro’s back, toes curling and his throat hoarse as he coursed toward his second orgasm. 

Shiro hissed at the scratch of his unrelenting claws, and Keith murmured an apology, but Shiro only grinned. 

“I like it.” he said, and Keith blushed even as he arched under him, a hand reached between his legs to rub at his clit. “Like seeing you lose yourself.” he said with a pointed look at his eyes. 

Keith’s teeth ached with the mild transformation, and he was certain Shiro meant how his eyes had gone as yellow, feral as his claws. 

Shiro moaned when he clenched around him, slowing his pace as Keith cried out and came. 

Shiro slowly fucked him through his orgasm, and then he gasped softly. 

“Keith…” 

“Mm?” 

“You kinda…um…” 

Keith couldn’t even think, let alone lift his head. 

Shiro’s flush deepened and he chuckled, “I think you squirted.” 

Keith blinked up at him, and then he shrugged. 

Shiro barked a laugh. “So it’s that kind of good, huh?” he surmised, looking quite pleased with himself, and Keith shoved his shoulder half-heartedly. 

“I guess it is. Are you done?” 

“Not by a long shot.” 

Keith hummed and then he pulled away again. 

“I like it better like this.” he said as he rolled onto his belly once again.

“You’re the boss.” Shiro teased, prying a finger or two inside him before his cock followed. 

Yeah. That was the angle. One hundred percent. 

Keith bit his lip against a moan, turning it into a husky whine in his throat. 

Shiro grabbed his hips and pulled him into his thrusts, and Keith grasped onto the ruined sheets with a feral yowl. 

…that was definitely a Galra thing. 

“Fuck.” Shiro muttered from behind him, and Keith could share the sentiment. 

He started to speed from there, desperation bleeding into his movements as he pressed Keith into the mattress and pounded into him. 

Keith could only sob in pleasure, rocking back against him the only thought in his head. Remaining full of his cock until he passed out was starting to sound like the best idea in the world. 

But that was wishful thinking. 

Shiro groaned and Keith keened when he felt him pulse, his thrusts slowing, a few more stuttering slaps of his hips against Keith’s ass. And then he was coming, thick and hot inside him. 

Keith’s jaw dropped at that, gasping as Shiro pumped him full, and then the both of them went lax. 

Shiro’s weight was both almost too much and just right as he panted against his back. 

“Good?” Shiro wondered. 

Keith grunted, and Shiro rolled off of him. 

“Sorry.” 

“S’okay.” Keith mumbled, shifting and then sighing. He’d remain on his belly, he supposed.

Getting up…yeah. No fuckin’ way.

“So…that’s it for you, then?” Shiro wondered, brushing Keith’s sweaty hair back from his face. 

“Mhm.” Keith nuzzled into the sheets, “I can’t feel my legs.” 

Shiro laughed and went to move him, rolling him onto his back and fetching a damp cloth to clean him up. 

“I liked it too.” he said as he wiped at Keith’s legs, “And I’ll say it again, I don’t care whether you are noisy or not…but goddamn.” he shook his head with a blush and a smile. “I’ve never heard you make sounds like that, before. It was…hot. Really hot. Had a hard time not busting prematurely.” 

Keith smiled lazily, moaning softly when Shiro massaged at his thighs. 

“Good to know.” he murmured. 

Shiro kneaded at his legs until he was starting to pass out, and he only woke to find that Shiro had gone to get dinner. He came into the room with a hot bowl of ramen, and Keith chuckled. 

“Thank you.” he sighed as he pushed himself up and against the headboard. 

“You’re welcome, baby.” 

“That was nice.” he said as he ate. 

Shiro bit his lip, cheeks reddening, and Keith giggled in delight. 

“It wasn’t even all that new.” he said. 

“It was for you, though.” Shiro said, “And I’m glad I was a part of it. I really am.” he reached for Keith’s hand, “Thank you.” 

Keith squeezed his hand in return, “You know, that isn’t all I had in mind.” he said after a few moments of silence. 

Shiro raised a brow, “Oh?” 

Keith debated his answer for only a few seconds. 

“Yeah, I actually had this idea of getting a strap-on….”

Notes:

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