Yes, this is happening. Congratz, you get to read this shameless smut. I wanted this to happen, and now it is.
Let's go.
Disclaimer: I do not own Undertale, which belongs to Toby "Radiation" Fox. Megalovania appears in two other works besides Undertale. Props to the people who know what.
Chapter 1 (And Possibly the Only Chapter Unless The Readers Want Plot)
The rut came just as it had every other year. We monster don't like to talk about it. Y'know, it is pretty personal to talk about, but I'll explain it anyway. Different types of monsters have it happen at different times, usually they all leave to their own hiding holes and wait it out or spend the day with their partners doin' their thing. Skeletons enter their rut about every fifty years so, it doesn't happen very often. This leaves me with a very big, slowly getting even bigger problem and it's called Papyrus.
I don't know how old he is, meaning I have to lock the doors everytime that day comes. I usually lock the front door after we eat, saying it's for my peace of mind when he gives me a funny look. He usually yells, saying that nobody would dare barge their way into the Great Papyrus' house, but he doesn't try to unlock it. After he goes to bed, I usually lock my own door and go to sleep only to feel like I'm dying of heatstroke the next day and having him pace outside my door in a worried state. I tell him to go outside and I'll be al'right, but he doesn't buy it. He even has Alphys come over to try and take care of me. He's a precious cinnamon bun.
Now, if you're paying attention one word should probably be sticking out to ya. Usually. This time, I forgot to lock my door. The minute I saw Papyrus, worried and frantic over how I looked, I almost lunged at him. God, the overwhelming heat... My magic was pumping through me in waves to the point I was shaking. I was locking up so many feelings at that point, I just wanted to let go and stop caring. Then, I felt it. Papyrus.
He was staring at me with a dazed and intoxicated look, completely relaxed. A minute ago he had been a wreck as he was talking to Alphys. He had been talking to her, when he suddenly grew quiet, watching me shake like I was having a seizure. Then he said something I could not grasp.
"I THINK I KNOW WHAT I HAVE TO DO. BYE, ALPHYS."
"N-no! Papyrus, don't hang u-" Click!
That was when I remembered something Undyne had told me in confidence. Sans was sick that day, dreadfully so. I called Alphys and asked her to check on him for me. I had not been feeling up for training or cooking that day, which troubled both Undyne and myself.
"Hey, Paps. What's the problem?"
"OH, UNDYNE! IT'S MY BROTHER! POOR SANS IS WITH FEVER AGAIN THIS YEAR. AND ALWAYS ON THE SAME DAY AS WELL! I, THE GREAT PAPYRUS, AM REALLY WORRIED FOR HIM!"
Undyne frowned before lighting up, "OH! He's just going through his rut, Paps! Happens to everyone!"
"REALLY?! HE'S GOING TO BE OKAY?" I hoped he was going to be alright. Sans is my dear brother, afterall. I don't know what I would do without him!
"Well, yeah. He should be okay, but it usually helps if they get out of their system."
"UNDYNE, I DEMAND YOU TELL ME HOW TO HELP HIM AT ONCE!"
"Wait. You don't know? About rutting?"
"NO, I DO NOT KNOW THIS RUTTING. WHO IS HE?"
That day, Undyne explained to me about this so-called rutting and that it should happen to me as well one day. That day appears to be today.
I woke to what I could only imagine was fire being injected into my bones, skull pounding as I rolled out of bed and got up. I did not attempt to change out of my sleeping wear, which consist of a shirt that said 'Jocboy', a pair of baggy shorts, and my amazing gloves and cape. I quickly checked Sans' room for the usual sound of snoring, only to hear the moans and gasps. Wowie, we were both sick! I knocked on the door and found him in much worse condition than I. His sheets were kicked off of him and his clothing consisted of a sweater riding up his body and exposing his spine and lower ribcage, his usual shorts, and a single slipper with the other being on the other side of the room. Calling Alphys, I was about to request she come over, when I stopped and began to feel strange. I remembered that Undyne told me about something like this as well. Creatures in rut like to do romantic things like touching and kissing. If that would help me, would it help Sans too?
Papyrus walked over despite the dull ache of his bones and pulled you into his lap. Your shaking grew and you slowly began rocking as Papyrus held you. Oh my God, he had no idea what he was doing to you! The dam of emotions would only hold for so long and Papyrus was doing everything to wear them down, which was not helping. His gloved hand was rubbing circles into your spine, making you whimper and rock harder. Call it anything you like, but a rut does something to your mind and makes you think anything could be okay. Even having sex with your own brother that you weren't biologically related to.
Papyrus huskily whispered, "Do You Like This?" Your bones began to rattle together faintly from the strain of holding back a rushed shout of an answer. What was he even doing!? Trying to hold yourself back was becoming too difficult. The next thing he said blew you away.
"Because I Really Like This, Sans. Please Don't Stop." You had been pratically grinding yourself against him in your state. You felt the flood gates open as you frantically began nuzzling the side of his face and your magic began leaking from you slightly. Your cerulean color flooded around the two of you and you faintly became aware of a stream of words leaving you.
"PAPS, I LOVE YOU! PLEASE, HELP ME! IT'S SO HOT! I CAN'T TAKE IT ANYMORE! YOU HAVE TO MAKE IT STOP! I LOVE YOU! I NEED YOU! I NEED YOU RIGHT NOW! YOU KNOW WHAT TO DO, RIGHT?! THEN, DO IT! PLEASE! Please... please?" You were aware of how you were shouting in his ear. Even though he didn't have ears...
"Sans, I Think I Know What To Do, But We Are Two Male Skeletons, So It Will Not Work." The way he said it with such conviction and worry made you 'bout crack up.
"Pfft. 'Male Skeletons'? Skeletons don't have genders, bro. We're what we wanna be."
Papyrus watched curiously as Sans slowly leaned his weight against him and shimmied off his shorts, exposing a magically crafted penis that had accidentally been made in his rush of magic. It glowed a cerulean just like the rest of his magic, but Papyrus could tell that wasn't just what he had made with his magic. He could almost see more past the cock. He moved his hand to touch what he could see, when Sans quickly stopped him and guided him lower. Papyrus frowned before heeding his brother's advice and touching around the area he presented him with. His quick exploration ended even faster as his phalanges slipped into a hole, making his brother squeak in surprise and begin shaking again.
A hole?
...
...
...
...
...
!
Oh! It was THAT hole?! What was his BROTHER doing with one of those?!
Then again, they were skeletons. With no strict gender, a skeleton easily chose its own gender based on its feelings.
"Paps, why'd ya stop," Sans whined as he rocked, making Papyrus' phalanges slip in more. Both of their breaths faltered at that moment as Papyrus' own bright orange magic activated. His magic, which went completely into making his penis, quickly disappeared after it got its job done. Sans' cock, which happened to be five inches, was at least an inch smaller than Papyrus who was also slightly thicker. At least, that was how much could be seen with Papyrus' shorts in the way. Papyrus began thrusting his fingers into Sans, realizing that he would have to stretch his brother out to prepare him.
"Paps, I want you already," Sans quipped in impatence as he rocked against the younger skeleton. Papyrus nodded in agreement as he pulled down his own shorts and began to line himself up with Sans, until there was a pounding on the door. It caught Sans by surprised when the sudden sound came from outside. He wondered for a breif second if it was Alphys, however he stopped thinking soon after.
Papyrus, using the distraction to his advantage, quickly thrusted into Sans and tearing a high-pitched yelp out of him. He watched as tears the color of his magic slowly beaded up in his eyesockets, scaring Papyrus greatly. Had he hurt him by doing that? Apparently not enough, because Sans began whining and bucking as he felt Papyrus inside of him. The delerium brought by the rut quickly reared its head again.
Alphys had quickly run over to Undyne's house and explained that both Sans and Papyrus were going through a rut. Male monsters in rut could easily hurt or even kill each other in their delrious state, making the two female monsters worry for their friends. Undyne, being the more atheletic one of the two girls, carried Alphys as she ran to the skeleton brothers' house. As soon as Undyne stopped, Alphys quickly jumped from her girlfriend's arms and knocked on the door.
The loud yelp from inside the building sprung the two into action, Alyphs scurrying out of the way as Undyne charged the door. The first time, Undyne bounced off the door with a sharp crack. The second time, she pushed against the door and the splintering sound of multiple pops filled the air. The third time, finally, led to the door bursting open and allowing the fish monster into the house. Alphys quickly followed her into the house, only to stop as Undyne jogged up the stairs. The sounds that were coming from upstairs didn't sound like fighting. The little, yellow dinosaur-like monster approached the bottom of the stairs as Undyne slowly walked back downstairs, a red blush spread across her face.
"PAPS!~" Oh. My. God. Alphys felt her own face flush bright red at the sound of Sans shouting like that. Undyne quickly walked back to the front door and quickly looked back at her.
"Do you want to go get some Nice Cream while they, Um, Finish up?"
Alphys quickly nodded as she followed her girlfriend outside. Undyne quickly blocked the door with a large cube of ice before the two left. They didn't want to let anyone else into the skeletons' house.
Neither of the two skeletons had been aware of the fish heroine knocking their front door down, nor had they been aware of her opening the door to Sans' room only to slam it shut again. Papyrus was too busy thrusting into his brother's tight heat and nipping at his neck. A particularly hard thrust caused Sans to scream his name and bite into Papyrus' collar bone. Sans' phallanges were wrapped around Papyrus' clothed shoulder blades as he moved back against him. Their thrust quickly became erratic as the pleasure and delerium became too much. Sans nearly screamed as he felt his orgasm overtake him, squeezing Papyrus as he released his cerulean fluids over his brother and himself. Papyrus quickly followed him a thrust later, his own orange essence spilling into and dripping out of Sans' vagina. The two slowly began to relax as the delerium disappeared.
Sans slowly blinked as began to grow more coherent and began to take in the situation he was in. Papyrus was inside of him, orange jizz was slowly leaking from him, and the two were painted in his cerulean seed as well. He felt himself begin to panic until he felt teeth clack gently against the side of his face. Papyrus pulled out of him, causing a whimper of discomfort to fall out of his mouth. Sans wrapped his arms around Papyrus' neck as the younger skeleton laid down on the even messier bed. Their magic slowly began to fade, dissolving into the air. Yet their fluids still clung to them and Papyrus growled slightly at the mess, causing Sans to chuckle lightly.
"AS SOON AS WE WAKE UP, I, THE GREAT PAPYRUS, DEMAND THAT BATHS BE TAKEN!"
"Heheh... Yeah," Sans tried to laugh off the comment, but began to sweat at the tension he felt in the air.
Papyrus sighed, "SANS, IS SOMETHING WRONG?" Sans blinked up at Papyrus and almost began to feel anger at the young skeleton. What type of question was that!? 'Is something wrong?' They just had sex! Of course, something was very wrong!
"We're brothers, Paps. Brothers don't do THAT together. It isn't right," Sans groaned as he rolled off of Papyrus, eyesockets squeezed shut.
Papyrus pulled his brother back into a hug, "IT DIDN'T FEEL WRONG TO ME, BROTHER! SO, IT MUST BE OKAY." This caused Sans to begin crying. He didn't know what to do! It wasn't okay and he knew it wasn't!
"SSSHHH. IT'S OKAY, SANS. PLEASE TELL ME WHAT'S WRONG."
"I-if an-anyone finds out about u-us, i-it..."
"NYEH HEH HEH! THEN WORRY NOT, MY DEAR BROTHER! NO ONE ELSE WILL FIND OUT ABOUT THIS."
"H-how do you know?"
"BECAUSE I BELIEVE IT WILL BE ALRIGHT!" This made Sans' tears slow as he looked up at his brothe- No, his lover. He sniffled a few more times before crawling out of Papyrus' arms. "HEY, SANS, WHERE ARE YOU GOING?"
"That bath you mentioned sounds pretty good. Do you wanna join me?"
Papyrus blushed, "WOWIE! THAT SOUNDS RATHER INTIMATE, SANS! ARE YOU SURE IT'S ALRIGHT IF I JOIN YOU?"
If Sans had any eyebrows, they would be cocked up in confusion, yet he had none. That didn't stop him from showing Papyrus how confused he was.
"Paps, stop being re'dick'ulous and join me already."
"BROTHER, I DISOWN YOU," Papyrus shouted as he leaped out of the filthy bed and followed his brother. Hopefully, the heat had passed without any more complications.
Now, it is your choice, the readers, if you want another chapter for this story.
Until then, stay determined, my friends.
EDIT: I just released how weird reading this would be without proper spacing. Sorry, amigos! :3