Sans was at least 800% sure that his brother was trying to kill him.

It hadn't been too long ago, perhaps a year, that Papyrus had somehow convinced him that yes, they could be together in a more-than-brotherly way and no, it wasn't weird. They had agreed on no funny business after Sans had nearly leapt a foot away from Papyrus after hearing him moan for the first time while they had been cuddling. It had been an accident, really. He had been beginning to doze off, nearly purring in contentment while they held each other on the couch watching some movie that MTT had made a few months ago (the guy was really churning them out nowadays, Sans thought. Just as well. It gave him and Papyrus more opportunities to find themselves like they were now.) He hadn't realized that his fingers had gone under Papyrus's nightshirt and brushed against his hip. Against the side of his skull, he felt his brother's soul start vibrating faster, but he paid it no mind. A distant part of his sleep-addled brain heard Papyrus call out to him, somewhat shakily, but he dismissed that too. He was probably trying to get his attention that it was time to go to bed. Snuggling closer to the unusual warmth Papyrus had always given off, he brushed his thumb affectionately against where his hand was resting. A breathy sigh and a hand coming to rest on his forearm caused him to clench his hand against Papyrus's hip, then he heard the moan. It was like he'd touched fire. He yanked his hand back and scrambled off the couch, the blanket across his lap tangling around his legs. The short skeleton didn't even have the mind to correct his balance and sprawled on the floor, quickly flipping on his back and staring down his brother with wide eyesockets. His brother…oh gods, he looked so…Sans gulped. Papyrus was staring down at him with wide eyesockets of his own, a red-gloved hand (gods, why didn't he ever take those off?) held up to his mouth and the other reaching for him. He had the most adorable blush on his face and he seemed to be trembling a little.

"SANS! ARE YOU OKAY?"

Sans made a concerted effort to calm down the racing of his soul, worried it'd start glowing on him here soon.

"y-yeah. what was that?"

Gods damn it. He looked so guilty now, his orange flush deepening in shame.

"I'M SO SORRY. I DIDN'T MEAN TO, IT JUST…CAME OUT. YOUR HANDS WERE SO GENTLE AND COOL AND…OH, SANS, PLEASE DON'T BE MAD AT ME."

Sans made quick motions with his hands, willing Papyrus to listen to him.

"nonono, paps. it's okay, i'm not mad, i just wasn't expecting…i'll be more careful from now on."

"OH. YES. OF COURSE."

Despite not being remotely tired anymore, Sans faked a yawn and stood, stretching his arms above his head. Papyrus felt his cheeks get deeply flushed again as his brother's shirt raised, exposing a small sliver of hipbone and spine. He looked down at his lap, where he was nervously wringing his hands.

"well that was too much excitement for me. i'm gonna turn in, paps."

Placing a hand against the side of Papyrus's head, he gave the crown of his skull a skeleton kiss and began making his way to the stairs.

"…GOODNIGHT, BROTHER."

"night, bro."

Papyrus followed him after a moment, and Sans heard the click of his brother's door closing as he leaned against his. He sighed softly and shook his head, going blue in the face as he cursed himself for the umpteenth time. Flopping down on his bed, he held his pillow over his face, clenching it for dear life as he tried restraining himself. He failed.

Both of them spent that night doing their best to keep their voices muted as Sans indulged his fantasies again and Papyrus explored his for the first time.

The curious thing about being someone's significant other and awakening your sexual desire is that you become hyperaware of them. Their position in relation to you, the way they move, the way they speak…the way they smell. Papyrus had practically locked himself in his room a couple of days ago, telling Sans that he wasn't feeling well. He told Sans that he didn't want him to come in, that he was afraid it might be contagious, whatever it was. He told Sans that he'd be fine after a couple of days. Technically, Sans mused, he wasn't wrong. He was pretty sure Papyrus's 'ailment' would be very, very contagious, not that his rapidly degenerating will put up any resistance to the idea. He knew Papyrus was lying through his teeth. The heady aroma that was saturating Sans's senses made sure he knew that.

There had been attempts to resist. On the first day, when he had first smelled the beginnings of his brother's heat, he had teleported as far away as his abilities had allowed, landing (somewhat fittingly, if you asked him) in the garbage dump. For a solid five minutes, Sans had freaked out, pacing back and forth, making strangled noises in his throat, even blasting one of the junk piles as his energy continued coiling. He had vowed that he'd find as many reasons as possible to stay away from the house. Camp out at Grillby's. Visit Asgore. Go bother Alphys. Anything. By evening, he had exhausted all the ideas he had come up with, and it hadn't helped that Alphys had had Undyne with her, the tall fish monster asking where his brother was.

"he told me he wasn't feeling well and didn't want to be bothered. i let him be."

If he didn't know better, he'd think Undyne would have speared him and hung him out to dry, based on her expression.

"Papyrus is sick? What the heck are you doing here!? You're such a dork, go take care of your brother!"

'oh, i'll take care of him alright…no, no wait, bad.'

"heh. yeah, i guess you're right. guess i'll go ahead and head out. see ya."

When he got back to the house, he was met with the sounds of his brother's loud moaning and cries of his name.

"if there is a hell, i'm in it," he muttered grumpily.

Resisting his instincts to go to Papyrus, he locked himself in his own room, spending the evening cumming repeatedly while listening to Papyrus tirelessly pleasuring himself.

Now on the second day, he held his hand against Papyrus's door, hearing his labored breathing. Something inside of him harshly gave way when he heard muffled sobs. He knew it hurt. He didn't want Papyrus to hurt, his own hesitation be damned. Firmly, he knocked on the door, hearing his brother shift inside.

"bro, i know you can hear me. i know what you're going through."

There was a second of silence. His voice sounded strained from overuse, and he couldn't quite hide the pleasure from his tone. He was probably touching himself as he spoke, and it made Sans want to just break down the door.

"YOU…AH-…YOU DO?"

"yeah. i can help you, paps. can i come in?"

Another moment of silence. Sans heard a tiny breathless gasp.

"Y…YES. PLEASE."

Bracing himself as much as he could, knowing he'd probably lose it, the older skeleton turned the knob of the door, pushing it open hesitatingly despite his mind's insistence that this was the best thing he could ever do. The smell of his brother was so much stronger without a barrier blocking him. A growl nearly ripped itself from his throat, but he clenched his jaw firmly, holding it in. His eyelights fell on Papyrus, spread-eagle on his disheveled bed, his face heavily flushed and orange tears escaping from his eyesockets. One hand was held up against his mouth, muffling his cries, and the other was stroking his member in short, jerky motions. His brother's eyes had locked with his. A wave of cold washed through Sans, making his hands twitch involuntarily and magic spark in his eye.

"I…I CAN'T STOP MYSELF, S-SANS. IT WON'T GO AW-AWAY NO MATTER HOW MANY TIMES I…AND IT-IT HURTS…"

He bucked into his hand, letting out a stifled moan.

"D-DON'T LOOK AT ME, PLEASE..."

His poor brother sounded so ashamed, even though he was probably maddened with lust.

"papyrus. why…would i want to look away from something so beautiful?"

He made his way to the edge of he bed, where his brother was biting down on his (still?) gloved hand, one pointed tooth threatening to break through the red leather. Sans reached down, gently pulling away the abused hand and wiping away his brother's tears.

He remembered his first heat. It…hadn't been pretty. He had gone and locked himself in his lab, half-insane with pain and lust, begging the imaginary Papyrus sitting in the room with him to fuck him, to kill him, to end his misery. The spectral Papyrus never listened, disgust warping his features into something unrecognizable. He had felt sickened with himself back then, full of self-loathing for thinking of his brother in a way that he was certain was unrequited. Oh, how wrong he was.

"look at you. i was so gone during my first time, and you're taking it like a champ. you can even still make complete sentences. my second day i was like you, screwing myself senseless, but there wasn't room to think, just room enough for me to call out to you."

His hands trailed down Papyrus's bare bones, scratching lightly at his sternum. His brother's breath hitched. The sound of his voice seemed to be affecting him, if the increased speed of his strokes from the corner of Sans's eye were anything to go by. He decided to keep going.

"i remember how much it hurt, how much i cried, how much i screamed. it was torture."

He settled one knee on the mattress, now looming over Papyrus. A single finger dragged down the tall skeleton's spine, causing him to moan loudly.

"S-SANS…"

"but you? you've held up so well. much better than i could ever have done. i'm so proud of you."

Both knees on the mattress now, Sans brushed the back of his fingers against Papyrus's jaw, his other hand going down and removing his brother's hand from his dick, the hand giving surprisingly little resistance. He wrapped his hand around the orange phallus, his thumb rubbing small circles around the head. Papyrus cried out at the contact, his hands fisting in the sheets beneath him.

"SANS!"

A smirk tugged at the corner of his mouth. He kept his hand still, his thumb still moving in circles. He grabbed the hand Papyrus had been using to stroke himself, bringing it up to his mouth and sniffing. It was like the most delicious food in the world had been shoved under his nose, causing his mouth to water. Slowly, he opened his mouth and took two of the digits in, swirling his tongue around them and tasting the concentrated essence of his brother on the leather. He couldn't control the growl that escaped his throat that time. His eyes were fixed on Papyrus, watching him writhe beneath him.

"paps, you taste incredible. i shouldn't have waited so long."

Papyrus whined pitiably.

"SANS, PLEASE. I-IT'S TOO MUCH, I CAN'T—"

Anything he was going to say was abruptly choked off as Sans began stroking him, the small skeleton biting down lightly on his fingers. He quickly found his voice again, short and quick gasps and moans filling the room. Sans continued nibbling on his brother's fingers, his canines grazing against the appendages and making them twitch. He could see Papyrus getting more tense, his free hand curling more tightly into the sheets. Oh, how he was looking forward to having his precious brother fall apart, again, and again. At the thought, he moaned around the fingers in his mouth, his flush deepening.

"SANS, OH S-SANS. I FEEL…"

The small skeleton sped up his strokes, taking Papyrus's fingers out of his mouth. He leaned down, his face stopping a short distance from his brother's. His eyes were half-lidded as he spoke.

"paps…"

The skeleton didn't respond, but he kept his eyesockets focused on Sans, waiting. He was so close… Sans adopted a commanding tone.

"scream for me."

As if hitting a switch, Papyrus orgasmed, screaming as thick ropes of cum spurted out and partially gathered on Sans's hand. Sans smiled

"good, good, you did so good."

Almost clinically, Sans lifted his hand to study the ectoplasm on it; knowing his brother was watching him, he let his tongue dart out, tasting his release. If he could purr, he'd be doing it right now. Papyrus let out a shaky moan at the sight, his ribcage still heaving with the intensity of his orgasm.

"O-OH MY GOD, SANS."

"have you tasted yourself, paps? it's incredible."

Sans could feel his higher intellectual functions shutting off one by one, as he continued licking at his hand. He'd held off as long as he could. Lowering his hand, he made eye contact with Papyrus one more time, silently asking for permission as he scooped one hand beneath his shoulder and the other beneath his hip. There was only trust in Papyrus's gaze. In one smooth motion, he flipped Papyrus onto his front and straddled him, running a hand down his vertebrae and stopping at his hip. He felt Papyrus shudder beneath him as he ran a finger across the curves of his hip. To think he had started this all because he had accidentally touched his brother's hip before. He curled the fingers of both hands around Pap's hips, pulling upward so that his lower half was in the air, level with Sans's. The tall skeleton had dug his fingers into the pillow his head was resting on, one side of his face flat against it and his exposed eyesocket squeezed shut. He was beautiful. Not wasting anymore time, Sans pulled down the front of his shorts and lined himself up with the hole in Pap's pelvis, feeling a slight pressure as the intangible magic that composed his innards pushed back. He held his place for a moment, shivering at the sensation, before he heard Papyrus whine beneath him.

"PLEASE…"

His control shattered. With a quick snap of his hips, he entered Papyrus, the younger skeleton shrieking and flinging back a hand to grab at where Sans was digging his fingers into his hips. His thrusts were hard and fast—some vague part of him scolded him, saying he should be more gentle for the first time, but the more animalistic side of him pointed out that Papyrus seemed to be enjoying it, and that fuzzy part was silenced, the primal side growling in satisfaction—and Papyrus was desperately trying to muffle his cries in the pillow, but Sans was having none of that. He wrapped the hand not being clutched for dear life around his brother's dick, stroking firmly.

"don't hide your voice from me, paps. too…fuckin good."

"M-MORE. SANS, I NEED MORE."

"so needy," Sans breathed "but your wish is my command."

Gritting his teeth, he let go of Pap's dick and hunched down, wrapping both arms around his waist and increasing the force of his thrusts. His movements were relentless, almost desperate in nature. He wasn't close enough to Papyrus. He could never be close enough.

"so good. so fuckin good. god i love you so much."

Papyrus felt that coil in his gut again and he nearly sobbed at the sensation, instinctively clenching around Sans.

"shit! Keep doing that paps, that's perfect, oh fuck.."

"I THINK I'M GOING TO…S-SANS, AH! YES, RIGHT THERE, AH, SANS~!"

He came again, cum splattering onto the sheets beneath him. The winded skeleton continued clenching, feeling Sans's rhythm become jerky behind him.

"hah, mnn, fuck yes, unh, paps, paps, so good, so…fuck!"

Sans's hips jerked once, twice, three more times before coming to a shaking halt, his entire body shaking with the force of his orgasm. He let his brother's hips go, pulling out gently and crawling up to his face, their mouths meeting with a *clank*. Papyrus eyed him dreamily, marmalade flush still heavy across his cheekbones.

"SANS…THAT WAS AMAZING."

The short skeleton chuckled to himself before giving a (mildly dishonest) regretful smile.

"that was just the beginning, bro."

Papyrus leaned up on one elbow, looking down at him somewhat worriedly.

"BEGINNING? YOU MEAN IT…IT DOESN'T GET BETTER?"

Sans shook his head.

"it took me at least 3 more days before i was back to normal."

His poor brother's eye sockets went wide.

"D…DAYS!?"

"i don't know, maybe it won't be as bad with someone helping you. i was alone for mine."

Papyrus groaned in despair.

"don't worry, paps. it won't hurt anymore. i'll be here to take care of you."

"YOU PROMISE?"

"i give you my word."

Sans didn't really remember much afterward, only flashes of imagery in his head—

His face buried in Papryus's neck while he rode him, his brother's arms wrapped around his waist-

Papyrus throwing his head back and crying out while Sans took as much of his dick in his mouth as he could-

Drawing a bath for his brother while the tall skeleton stood to the side with shaking legs-

Him wailing as his brother desperately thrust into him against the shower wall, his right eye glowing a gorgeous orange-

Papyrus calling after him in fear as he tried leaving the bedroom to go get him food. He hadn't known that would happen-

Him discovering his brother's love of honey as it was licked from his collarbone-

Him using a damp cloth to lower his brother's temperature while whispering loving things to him-

Him chanting Papyrus's name like a prayer while he fucked him on the couch-

His brother adorably nuzzling his shoulder while they both dozed off in his remarkably clean bed on the fifth day; he was okay with being the little spoon for once-

Sans's memories were clearer when he awoke on day 6. He sat up, rubbing at his eyesockets, then looked down at the still sleeping Papyrus. A gentle smile flitted against his features as he thought about how tired his brother must be to still be sleeping at what his internal clock deduced was eleven in the morning. As delicately as he could, he extricated himself from Papyrus's arms and took a shortcut down to the kitchen to pull a couple of toaster pastries from the pantry. It wasn't the heartiest breakfast, but he didn't want to poison his brother with his shitty cooking.

When he got back to his bedroom with the toaster pastries and a glass of water in hand, he found Papyrus sitting up in bed, a groggy look on his face.

"hey bro. got you something to help you get some energy."

The taller skeleton looked up, eyeing the pastries with mild distaste.

"SANS, THESE ARE NOT IDEAL FOR ENERGY."

"sure they are. sugar is plenty good for energy. besides, it's all i could come up with. i'm not a star chef like you, paps."

Papyrus glowed a little at the praise.

"WELL, I AM PRETTY GREAT—"

He stopped midsentence and eyed the pastries again, a little less disgusted than before.

"THANK YOU, SANS."

"anything for you, paps."

And he meant anything.