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When it started, they hadn't noticed.
All it was, really, was the little things. They hadn't noticed, no one really had. They didn't notice the way they'd started attentively window watching, or notice once they had started giving each other little shoves on their way to the kitchen, or notice even when fighting over space on the couch. They hadn't thought that was odd. Siblings fought all the time. Over what? Hell if they knew.
As the day stretched out into a week, it became a bit more noticeable.
Kinda.
He was leaning stomach-first into the couch, facing the window. Phalanges, tinted blue with life tapped impatiently against the window sill. He'd been watching for a while, most people by now just crossed the street to avoid walking in front of their house. Sans sighed. He was jittery lately, and the evasion only seemed to agitate him more. Aggressive thoughts akin to “I thought this was a monster friendly neighborhood!” As well as “Fucking assholes- getting away.” Ran through his mind almost constantly.
Eventually, he perked up, seeing someone walking their dog down the street. Sans scrambled to the door, he unlocked it and stood on his tippy toes to see through the small window. Sans bounced on his heels.
The human was huge, they looked like they worked out but also looked unable to lose any of the fat they had stuck to them. Easily over 200 pounds. They walked a dog that resembled more like a mop, medium in size.
The small skeleton waited until the human’s first step onto the concrete in front of his house before ripping the door open and running onto the yard screaming insults. The man was startled, to say the least, by the loud noise.
Sans walked closer and stood in front of the human. He grew quiet.
...
“Get away from my fucking house.” He growled.
Sensing the hostility, the living mop growled back. “Fuck off!” Sans screamed at the dog, then began barking at it's owner. The dog whimpered before barking even louder at the unhinged monster.
The person took a step back, sneering in confused disgust at the behavior. Sans took a step forward, panting. His eyelights were wild and his voice was cold. “ Leave. ”
The person’s face reddened angrily. They placed a finger on Sans’ chest, but before they could tell him off, his hand was grabbed and he was tossed on the road.
The skeleton watched as the human scrambled off the road and hurriedly went on their way, dragging their enraged dog with them. Sans stuck his tongue out when he noticed them giving him the finger.
When he had noticed Toriel watching from the other side of the street, he simply waved before going back inside his house. From where she was standing, she could see his eyelights scanning the sidewalk from the window.
The second instance wasn't that big of a deal, the brothers felt. They had just begun walking into doorways at the same time, is all. During one of the big “monthly monster reunions” (and after Sans had an… interesting chat with the queen) Burgerpants watched them stare at eachother for a full minute before they both tried to go through the door at the same time. The feline monster felt his hair bristle slightly at the action. The fuck?
Papyrus shoved Sans out of the way and Sans shoved back. The smaller skeleton barely registered being pushed into the cat monster at the time, all his focus locked onto his brother. They both growled and their jaws snapped. Burgerpants, trapped watching from the sidelines.
Luckily enough, there was a calling for cake before all hell broke loose. The brothers walked as they normally would towards the kitchen, leaving an obviously frazzled cat monster in their wake.
It wasn't until Sans caught himself considering actually pissing on the couch that he realised something definitely was not right. The protectiveness and hostility between the two brothers couldn't be natural. It couldn't be. “Probably that asshole’s fault.” The small skeleton mumbled to himself.
Sans sank into the worn-out cushion if the couch, groaning. They probably looked like psychopaths.
A red gloved hand reached his vision and he growled when he realised it was touching his couch. Papyrus ignored him. “Why so glum, brother?”
Sans blinked a few times, snapping out of his hostile mindset. “We’re in heat.” He blurted out.
“...”
“...Pap-”
“Yes I heard what you said, brother but I'm afraid I simply do not have time for any shenanigans. I have a very important meeting with Undyne today involving the planned capture of the mysterious monster killer. It's urgent that I go, lest I look suspicious. I'm already suspect enough, Sans.” Papyrus frowned, hand sliding off the couch onto his hip. His face twitched a bit, annoyed at the thought of missing the possible confirmation of his immunity of suspect to the case.
Sans felt his face twitch at the way Papyrus said shenanigans . Like the destruction of everything in their- his territory - house didn't matter. He scoffed. “Yeah bro, this ain't just something you can ‘handle later’. If you go to that meeting someone's going to piss you off and you'll do something you'll regret....” The soft, brother-like tone the older skeleton usually had was starting to waver, slowly twisting into something more commanding. “And if you kill someone, guess what, it ain't gonna help your case.”
The tallest brother gripped the couch, but gasped as it was immediately smacked away by his brother. A low growl burned the back of his throat. “Then what do you suggest I do? Mr. Smartypants?”
By the end of the sentence both brothers were growling openly. Their hands played a violent game of “who owns the couch” until gloved phalanges sharpened and ripped through the fabric. They locked onto one of Sans’ wrists and a wave of silence caked onto the thick tension of the air.
The older brother shook his arm around, trying fruitlessly to get Papyrus’ hand off him before snapping his jaws and speaking. “I suggest you let fucking go of me and hide in your fucking room before I kick your ass. ”
Barely bothered by the threat- it was just his heat talking- Papyrus continued to push. Holding his brother's wrist tightly, his other hand securing the free one, Papyrus snorted. “You couldn't even if you wanted to.” He spoke, sharpened teeth retracting threateningly. “Remember these, brother?”
Before he could react with more than widened eyes, Papyrus was thrown off of his brother and off of the couch with a large surge of magic. A quiet crack sounded loudly through his skull and pain blossomed at the back of his head. He leaned back into the wall he was thrown into and looked back to the couch with wide eyes.
A pair of sharpened phalanges tore through the side of the couch as they helped pull their owner up.
Sans was snarling, mouth open as his bones made horrible creaking noises. Unused, but still very sharpened teeth unsheathed from their dull counterparts. “Go to your fucking room. ” One eye glared at Papyrus, bright yellow and blue, burning with fury.
The younger brother jumped. Though his injury was pressing him to attack and do something . He was snapped away from his heat-induced trance. “...sans?” He spoke quietly. “Sans calm down, brother.”
A growl was his only response as Sans stalked off the couch and began walking his way. He was still locked in the feral mindset.
Papyrus scrambled a few feet away and attempted to get up so he can run upstairs to his fucking room and not make whatever mindless creature his brother was more upset. A wave of dizziness hit him hard and he collapsed back onto the floor, his head pounding. He couldn't clear his mind properly.
He hadn't noticed his teeth and claws had retracted until his grip on the wall had been lost. His bones instinctually started rattling- whether or not it was in surrender or in aggression, he had more important things to worry about. There was only one thing he was willing to try in order to get out of this situation.
Sans’ shadow loomed over him, the blue and yellow from his eye giving Papyrus’ bones a soft glow. The younger brother whimpered pitifully. Small orange tears fell from his eyes. “S-sorry…” The tears stopped falling and Papyrus coughed awkwardly- knowing he was going to regret his next choice of words almost immediately- before choking out his next move. “ Alpha. ”
“...” Sans froze and when Papyrus looked up, his brother's eye lights were back to normal. His bones stopped rattling when he recognized the spark of clarity in Sans’ expression. Oh thank god .
“...Pap-” Sans snorted. Phalanges- no longer claws - covered his giggles.
And before long, Sans was fallen over on his side, wheezing and howling with laughter. “Pffff- p-pAP holy fuck! Ahaha… p-pap I can't blah- br-breATH!”
Honestly offended, Papyrus sighed. “...sans.”
Sans choked on his mirth and began coughing between his excited bouts of laughter. “H-hold *snort* hah! H-hold on br-hehe-bro!”
“SANS!!!” The younger brother shrieked.
The oldest brother held out a finger, catching his breath between giggles. It was at least a minute before he put his hand down, still a bit breathless. He coughed once before looking his brother in the eye, trying to wipe an entertained smile off his face.
“You finished, brother?” At Sans’ nod, Papyrus continued. “What the fuck.”
“Whaddya mean?” Sans frowned.
“EXACTLY WHAT I SAID. YOU THROW ME INTO THE WALL, SHOW ME THAT YOU'VE GOT THE-” Papyrus retracted his predatory features. “SAME NYEH! SAME STUFF I DO! THEN YOU WALK OVER HERE LIKE SOME SORT OF CREEP THAT WANTS TO EAT ME!
“AND THAT'S MY JOB. I'M THE CANNIBAL! YOU'RE NOT ALLOWED TO DO THAT! THAT'S STEALING!” Papyrus shouted, becoming more tense with each word. His skull pounded, the tension doing nothing for his headache.
Sans snorted, ignoring his lingering anger. “Ok.” Slowly, his grin became more mischievous and Papyrus glared in return. He scooched closer to his younger brother and sat beside him. When Papyrus tried to scooch away, his shoulder was grabbed and he was pulled into a hug from his older brother. He sighed, submitting to the hug. Due to his large frame, he had to basically lay his torso over his brother as his legs sprawled uselessly on the ground.
He felt himself growl lowly before Sans pinched him. “Owie!”
“What ya mad about, bro?”
“I hate hiding away in my room.” Papyrus grimaced. “In the moment I had thought that maybe if I had beat you, you'd be the only one that had to hide away in his room while I'd get the rest of the house! Nyeh heh heh!”
“Zzzzz”
“ARE YOU SLEEPING?! THE GREAT PAPYRUS HAD BETTER THINGS TO DO THAN LAZE ABOUT!” The younger brother screamed, thrashing around in his brother's embrace.
“Omega tax.” Sans explained.
“OH!!! MY!!! GOD!!! WE'RE NOT EVEN WOLVES I ONLY SAID THAT SO YOU WOULDN'T KILL ME. I WANT TO GO TO MY ROOM NOW!!!” Papyrus struggled harder, but Sans’ grip just tightened and he huffed.
“First of all, I think you meant to say ‘o-me-ga’ not ‘oh my god’. Second, you should really think before you g’omega terminology mistake, bro.” Sans laughed. It wasn't two seconds before the skeleton choked. “Are you licking me?!”
Getting another lick in response, Sans shoved his brother away. He shivered. “I can't believe you went there.”
Papyrus huffed, picking himself up from the living room floor. “The great papyrus would go incredible lengths not to laze about. Plus, how are you going to explain yourself while you're sleeping?”
Sans shrugged. “I'll do it after we're done our heats. Gonna be hard explaining anything if all I can think about is being angry and…” Sans suddenly blushed before he cleared his throat. “...yeah.” And with that, the small skeleton teleported away.
Papyrus growled, frustrated. “SANS!!! GET BACK HERE!”
“...SANS???”
The tall skeleton held the back of his head and winced. He stumbled to his room and pulled out a jigsaw puzzle. He didn't really want to solve it, but he felt he should wait a few hours before resting due to his injury. As he fit piece to piece, he began to wonder
what was Sans keeping from him? AND WHY DID HE LEAVE HIM ALONE WITH A HEAD INJURY? WORST. BROTHER. EVER!!! NYEH!