It just came into mind randomly -_- in the first few parts, you two are only 18. Also, there are some rather... Interesting.... Words later on. So warning I guess? Even though they are censored.
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Your pov

You sighed sadly, putting a hand over your chest as you heard creaks and moans from sans' room. You looked to the side as small tears pricked the corner of your eyes. This wasn't the first time though. He had done this in the past when he thought that you were gone. You were but you always come back to this. You sobbed quietly. Why? Why did he do this? You should have expected that monsters like him don't know what real love is. You dislike him but the feeling quickly disappeared. You sighed shakily. You just can't dislike him forever. You knew that you will just end up forgiving him. You can't do anything about it. You were just too forgiving. You thought for a moment, trying to wipe the tears that are falling down your cheeks. You stood up. You can't hate him but you can avoid him. You walked to your room. You almost never share rooms. Well, not when the first few months of your relationship passed by. You went in, glad that the walls were soundproof. You took a suitcase and some bags. You packed your clothes, things, etc.

Your room was close to empty. Good thing that you don't really have that many stuff. You closed the suitcase and took your coat, beanie and scarf. It was, like, -2 c right now so you needed those. You slightly teared up. The scarf was a light lavender, the one that sans gave you. You grabbed boots and put them on. You opened the door and went out. Sans' room was silent. They were probably sleeping. You went to the living room but you fell to your knees in the middle of it. Your soul ached. It was begging you to stay, to just wait until he realized his mistakes. You still love him even though he probably doesn't. You stood up and held back the urge to stay. You gripped the door's handle and opened it. The white snow fell down as the children happily played. You looked back into the house one more time before going out, slamming the door a bit too loudly due to frustration when your mind started to be clouded by doubts. You walked for a little and out of the street. You then called for a taxi. The man started driving. "Where are we going today ma'am?" You looked down, letting the words spilled out of your mouth before you can think.

"In the airport..."

Sans' pov

I woke up due to loud slamming. I yawned and sat up. I l. trying to gather my bearings. I saw (random girl's name) beside me, sleeping. I smirked and went out of the bed. I got dressed up and I picked her up, teleporting her to her house. I teleported back and opened the door to find the house quiet and empty. Too empty... "(Y/n)?" I called out. No answer. The silence was unsettling. I forced a small smile on my face. Maybe she's still not home? I looked at the clock. She should be home about an hour ago! I looked around. She doesn't go home late. I looked at my phone. No messages, no missed calls. I then went to her room. My face went pale. It was empty. Her clothes, books, her things are not here. "(Y-y/n)?" I called out, nervous. No answers. I ran to the doorway but froze when I saw a few glass shards. I looked down and saw a picture frame. We were both in it, in the park, happy. I picked it up. It was from the first few days of our relationship. The glass was broken as well as the frame. It was in two pieces actually. At one side, there was (y/n), at one side, there was me... The old me anyways... I know that I'm not the same person anymore. (Y/n) must have found out. Purple tears stream down my cheekbones. Why? Why did I do this? I went back to my room, dropping the forgotten frame. I took my long-sleeved jacket and a shirt that is identical to the one I'm wearing right now, except that it's not a crop top. I went out and tied my boots. It crunched as it made contact on the thin layer of white snow under me. I ran and ran, calling her name in the process. After a few hours, I didn't find her. I fell to my knees, purple tears falling faster. I could only cry as the sun set. I cried and teleported back home. I sat back on the couch, the silence consuming the house.

...

The house is more soulless and empty without her. I could only imagine her sad and broken face, looking at me. Eyes, filled with tears as her soul getting chipped off by betrayal until she disappeared. My soul ached. What have I done?

Years later...

Your pov

You went out of the apartment, using the elevator and exiting the establishment. The autumn breeze hit your face. You smiled as you put the letter in your sling bag. You were going to visit your old country again! It has been 5 years since you saw it! You got on your bike, going to the ariport. In this country, vehicles aren't allowed. Well, except for airplanes so, you learned how to ride a bike. You finally arrived after a few minutes. It wasn't that far. You went in but not before seeing your best friend, (f/n). They saw you and smiled. "(Y/n)!" "(F/n)!" You both hugged. It has been months since you saw them since they had to go on a vacation somewhere. You let go. They looked at you with teary eyes. "So your going huh?" You nodded. "Well, this is goodbye! For now!" "I guess it is." You responded. Before you can strike up another conversation, the speaker spoke up. It said that your plane was leaving. You looked at them. "Well, gotta go! Bye! Take my bike home for me!" You winked at them playfully. They chuckled and nodded.

You sat on the comfy chair, waiting for the plane to leave. After a few more seconds, it took off. You saw the clouds and birds went by. You sighed, listening to the music in your phone. You were excited, but... You got your sling bag and took out a picture of you and sans. You smiled with a bittersweet expression. You weren't sure how to respond when you actually see him. Maybe he got somebody after all those years? Your not even sure if you will see him. If you do, what will you say? I mean, you did just left him without permission but you had a pretty valid reason to. You still forgive him but, you are just waiting for him to apologise. I know, sorry isn't going to make up anything but for you, it will. You just can't dislike and forget him even after all those years. "Umm... Ma'am?" You jolted, surprised. You looked to the side to see a flight attendant. "I'm sorry if I startled you but I was asking if you would want some snacks during the ride." You let out a breath of relief. "Yes, I would love some. Thank you." She smiled kindly at you and handed you a bag of pretzels. Then she went off. You looked out the window, getting lost in your thoughts again as you ate the pretzels.

Sans' pov

I walked in the park with pap and the others. I had a smile on my face. You probably think that I'm doing alright now, right? No. I'm just trying not to show my grief to the others. Inside, I'm all broken, tangled, scarred, depressed. I miss her dearly. Late at night, I still cry, regretting my actions. I think they still notice some differences though. I don't talk and make puns that much, I trap myself in my room more often, I got less inspired to move, I space out more often, I wore more non-revealing clothes, yeah, you get it. While I was frozen in place, trapped in my thoughts, I got pulled back by my brother. "BROTHER! WHAT ARE YOU STANDING THERE FOR? COME ON!" I looked at him and gave him a small, forced smile. "i'm coming bro. just a sec." He scoffed as he ran back to the group. He's still as oblivious as ever but not innocent. Just enthusiastic. I took my phone out and looked at it's cracked surface, caused by me throwing it in sadness in one of the nights. I didn't mind it much. I only looked at my lock screen. It was (y/n), sticking her tounge at the camera, well, she was sticking it out at me, while having ice cream on her nose. I chuckled at the memory.

Flashback

I paid the guy and went back to (y/n). She was happily eating her ice cream. Then, she got some on her nose. She didn't notice it though. I chuckled. She looked at me rather cutely. "What?" I pulled out my phone and aimed it at her. She stuck her tounge out as I took a picture. I walked over at her and licked the ice cream on her nose. She blushed as I laughed. Then, she chased me, I ran and ran. I then tripped and fell into a pond. She laughed as I rose up, wet. I got out and she took out a handkerchief, trying to dry me off. "Be careful next time, alright?" I nodded. She kissed my cheek. I blushed. "Payback." I looked away, chuckling bashfully.

Flashback end

I didn't notice the tears streaming down my face until it dropped to my phone. I also didn't notice the group walking towards me, mostly running towards me, seeing my tears. "SANS! ARE YOU ALRIGHT?" I tried to wipe my tears off. I looked away, not able to answer. He looked at my phone and saw the picture. He sighed while the others tried to comfort me. "Sans, is it her again." I nodded. Frisk hugged me. "Sans. Get over her. She's not worth your time." I looked at them, anger now replacing my sadness. They let go when they saw it."no! she IS worth my time! the one that doesn't deserve anything is me! i'm the one that cheated on her countless times! i'm the one that let her down! i'm.... i'm the one that...." I trailed off as I cried, falling to my knees. Frisk sighed. "Right... Sorry." Toriel then talked to her about something. My eye lights disappeared. All that was left were dark, hollow holes. The others were a bit creeped out. "i just wish that I could have been there for her..." I muttered. I then fell silent after that. "I t-think we should g-give him m-more space..." Alphys said. The others agreed as they went off, not before looking at me for the last time. After a few minutes, I just decided to sit on a nearby bench. I then heard a few footsteps. I looked up and saw a few humans. "Well look who it is. A sl*t." They laughed as I just looked away. "Awww! What's the matter? Your partner left you? Must've thought that you weren't worth her time." "s-stop..." I muttered. "So the wh*re can talk? What more things do you know than ramming your d*ck to other people's *sses?" They circled me. "Well, let's find out." The others behind me held me up as the others beat me up. I stayed motionless. I didn't struggle, scream, groan, call for help, nothing. I just took the hits.

0.6/1 HP

"Sl*t!"

0.5/1 HP

"Wh*re!"

0.4/1 HP

"B*tch!"

0.3/1 HP

"F*ckboy!"

I let them call me names. What was the point in struggling. I felt like I deserved it. Then, my vision got a bit blurry.

0.2/1 HP

"Hey! Stop!" The others looked at the person. Their conversation was blurry.

0.1/1 HP

I blacked out.

I groaned at the slight pain that I was feeling. I struggled to open my eyesockets. When I finally opened them, I shut it closed again because of the bright light. I rubbed my forehead as I tried to sit up. A hand made me go back down again. I opened my eyes as I looked to the side. I saw a blurry figure. My vision still didn't work well it seems. Before they can talk, the door bust open, making me flinch in shock. "BROTHER! YOUR OKAY!" I recognized Papyrus' voice. When he looked to my side, well, it looked like he did, he froze. He fell silent. He then walked over to them. "Sans. We will be right back. I just have to talk to them." I nodded as they walked in the kitchen. I noticed that I'm back at my and pap's house. I looked down at myself. I looked really injured. I feel like I broke a rib or two. My cheek has a bruise, which I found out by accidentally touching it and it hurts. My ankle was twisted as well as one of my arms. They all had bandages on them. I stared at the wall in silence, my vision slowly clearing up. My breathing was ragged. Dang, they really did a number on me. I properly laid down, making myself comfortable before falling back asleep.

I woke up to a slight touch on my arm. I opened my eyesockets and widened them. I fully stood up, not feeling the pain in my torso. I can't believe it. (Y/n) looked at me, shocked. "S-sans... Your not supposed to be up yet!" She tried to make me lie down but I just hugged her, sobbing. "(Y-y/n)! I-i...." I just sobbed and hiccuped, not able to form any words. She hugged back comfortingly, running my back. We both stood there in silence, only the sound of my sobs were heard. "Sans, I really think that you should lie down now." I sighed and let go of the embrace that I wish would last longer. I laid back down, now feeling the pain in my torso. I groaned slightly in pain. She looked at me, worried. "Try to stay still sans. Just wait there." She stood up and went into the kitchen. It was silent until she came back. She came back with sone pills and a cup of water. She made me take the medicine. I felt my wounds getting healed a little. I assume that those are some healing pills that us monsters made. (Y/n) then looked away. "Sans..." I looked at her. "I'm sorry... I'm sorry that I left you. If I hadn't, then I could've defended you, you wouldn't have let them beat you." She looked down guilty. I frowned. "no c- (y/n). it's not your fault. it's mine. i'm the one that screwed up and plus, i'm the one that let them beat me up so don't be so harsh on yourself just because of this lazy, excuse of a boyfriend." I can't help but let out an insult towards me. (Y/n) just looked at me like I had just killed an infant and ate it's rotting corpse right in front of her. Well, maybe that's a bit too extreme. She held my cheek and made me look at her. "Sans, please don't say that to yourself. Sure, you messed up but you don't need to beat yourself up because of it. You might not think that your the best but at least you actually looked back and regretted it. That's what makes you a good person." You smiled and kissed him. He froze, clearly not expecting it but he kissed back. He put a hand on your chin and held it, not wanting it to end but you separated, making him whimper a little. You chuckled a little as you stared back at his eyesockets. His hand moved to your cheek and rubbed it with his thumb. You leaned into his touch, nuzzling his hand a little. Sans looked away, blushing but a small smile is still on his face. Your eyes closed, trying to enjoy the warmth he emitted. You held his hand with both hands while you opened your eye a little. His cheekbones were full on purple. "gosh cupcake, your just so... cute..." He muttered. You pouted when he called you cute. He chuckled. You gave him a playful glare and stuck out your tounge. He stuck out his in response. You, blushing at your own idea, slightly licked his tounge. He blushed profusely and quickly put his tounge back in his mouth. You did the same and hid your face in your hands. Sans recovered faster than you and smirked. "hmm... i wonder what else that tounge can do..." Your blush, somehow, increased. You let out a small yelp-like sound. Sans laughed softly. After that, the day passed by with lots of blushes, teases, cuddles and kisses.

It has been 8 years since that incident. You forgived sans, of course, when he apologized. He still apologized to this day even though you told him it was fine. He made it up to you in those 8 years. He would always give you attention, this includes him making time for you, lots of cuddles and kisses, which you adore. He also managed to pamper you like a queen. Though you said that it was fine and he doesn't need to do this, he said that it is fair if he did because of what he did to you years ago. Eventually, you both got married and had a child. (Child name) was 7 years old as of now. Now, they were on your lap, listening to you as you told them a story. They were a skeleton with your personality. Unfortunately, they were mute but it doesn't change your opinion on them. You and sans still love them equally. You closed the book as they clung to you sleepily. You chuckled. "Come on (c/n). Time for bed." Their signs were sloppy. You almost didn't understand it. "But I don't want to!" You shook your head and carried them and went to their room. "If you don't, the bed bugs will get you!" You learned that the monsters use a different term for bed monsters since it does sound offending to them. You find it funny but you don't really judge them. You put (c/n) on the bed as they yawned and nodded, them believing that there ARE bed bugs that will haunt them. You find it adorable. They shut their eyesockets, their (e/c) (normal white if you have black pupils like me :3) eye lights flickering before getting covered by their eyelids. You kissed their forehead and put the covers on them. "Goodnight (child's nickname)..." You turned their lamp off as you glanced at them one more time before going out and shutting the door. You sighed and smiled. You also have a surprise to tell sans. You hoped that he'll like it. You went to the kitchen and got a cup of water only to feel hands on your waist. You chuckled as sans laid his head on your shoulder. "hey cupcake~. how ya doin'?" Seems like sans is back from work and no, he got another job. He quitted his stripping job in grillby's. Instead, he worked as a waiter there since grillby insisted him to. You smiled at him. "I'm fine. (C/n) didn't want to sleep but I got them with the bed bugs trick." He chuckled. "How about you?" You added. He sighed. "busy as always but I'll never be too busy for you~." He missed your cheek. You blushed. "You sure that it's not too much for you?" You asked, a little worried. "it's alright sweetheart. nothing I can't handle." You looked away, a small but worried smile on your face. He senses your worry. "what's wrong? you seem worried." You chuckled nervously. "Well, I have something to tell you and I don't know if you will like it or not." This catches his attention. "hey, it's alright. you can tell me anything. i won't be mad." You sighed.

"I cheated on you with your brother-"

Technical difficulties XD

Take 2

"I hope that you don't mind another child running around this house." His eyesockets widened. "y-your pregnant again?" You nodded bashfully. His arms move up to your torso as his hold tightens. In other words, he's hugging you. He nuzzled his skull on the crook of your neck as his smile grew. "of course i won't mind! i'm actually quite happy about it!" You sighed in relief. "i wonder, what should we name them?" You thought for a little. "How about (second child name since I can't think of anything)?" "sounds perfect." Sans says as he lets you finally drink your cup of water. He then carried you which catches you off guard. "E-eh?!" You said as he walked to your shared room. He opened the door and put you on the huge and soft bed as it's softness engulfed you. He shut the door closed as he immediately went beside you, cuddling you. You faced him as you kissed his forehead. He looked down at your stomach. "i bet that they are going to be as good looking as you." You blushed and turned away from him, embarrassed. "S-sans!" He chuckled. "what?" You huffed playfully. He put his arms around your waist while your legs got tangled with each other. Your hands intertwined with one another as you leaned into his warmth. He does the same as he turned off the lights using his magic. "I love you sans." You muttered, slipping in and out of sleep. "love you too sweetie." you smiled. Papyrus was right. Sans really would make up for his mistakes. Your glad that you got back with him.

Gosh dang why the heck are they sO ADORABLE--?! Anyways, I'm back from my tomb called author's block -^- . I'm not sure if I made lust a bit ooc but hey. I was craving some bittersweet shhhhhhhhhhhh- *sees ink glaring at me* -hhhhhhtuff. Yes, shtuff. Don't correct me. Now, I'm sorry if the other chapters, especially the requests, will take long. It's just because I have no ideas for them. Also, should I make a deltarune x reader oneshot book? What do you guys think? Comment if I should. Anyways, boi potato chips! :3