Yandere!Gaster X Reader: My Beautiful Experiment

Grillby's

"The things I'd do for you kid" sans whispered so you couldn't hear it "huh?" "I said the things you want me to do kid" y/n smiled "yeah well when we were younger I took care of you and papyrus now I guess it's you take care of us now huh?" Y/n asked and she relaxed with her head on sans shoulder as they walked to grillbys. But a certain Gaster was snarling at this viciously, banging his hands on the portal and scratching at it with his hands. He wanted to KILL Sans. But the duo just felt an incredible chill as wind rolled by. Y/n shivered at the uncommon wind, but just shrugged it off. It was just wind after all. But that didn't stop her from greeting everyone she would meet with a kind smile. Especially the kids. The kids all loved Y/n. "Y/n can you come play with us," an armless monster known as Monster Kid asked, looking at her with hope filled eyes. Giving them a small smile she said, "Not now I gotta go to Grillby's and then I gotta hang with papyrus." Seeing them sad she cracked, "Okay! After I hang with Paps! I couldn't leave ya out here, snow joke~" "Yo! Y/n agreed to play with us guys!" Monster kid yelled as all the kids cheered at the news. As the kids were cheering and y/n was talking to them sand looked over at where the wind came from and winked 'looks likes she's mine now dad'Gaster practically hissed at him. So he was actually TRYING to take his Y/n from him?! 'Two can play at this boy,' he thought sending him a glare, 'Two can play!' Looking at Sans Y/n saw him staring at nothing placing a gentle hand on his shoulder, "You okay Sans? You. . Seem to be having an intense staring session with that plant there." She giggled at this thinking it was funny snickering, "Maybe we need to get to the ROOT of your problems~?" "What can I say kid I like flowers IRIS my case" sans said and winked at her. Laughing "hey I'm close to grillbys so if you want to admire the flower then I can actually tell grillby that you are ready to pay your tab AND Mr and Mrs dogs" y/n said as she ran towards grillby's leaving sans to register what she said. She ran off in double fist pumped victory, "Mwe heh heh~! That was so funny~! Mwe heh heh~" But not before she tripped and fell flat on her face over nothing but air. "Ow," she whined, she had bumped her head on a tree when she fell. She wasn't damaged but it still hurt. Looking around she wondered what had tripped her. it almost felt like a hand or something. She was confused."W-what did I even trip on there's nothing there unless... nah napstablook wouldn't do that" as y /n was thing of what she possibly could have tripped on she didn't notice gaster trying to put his hand on her shoulder. But before he could so that she was lifted into the air "gotcha kid geez you're right I do have to look out for you other wise you'll trip on nothing" as y/n stuck out her tongue at him he once again winked at gaster and mouthed 'sans: 2 gaster: -1000'Gaster could not believe it. It was HIM who stopped her from hitting the tree. But noooo, Sans comes along and picks everything up. Just like ALWAYS. But his Y/n, ahh~ He had discovered what his feelings were long ago. Now he wanted her. Damn this void for getting in the way! And damn Sans for being in his place!! But Y/n was oblivious to all this, and looked for who Sans could be winking at. Finding none she asked, "You gotta imaginary friend your not telling me about?""Yep and you wanted grillbys right?" "Yeah let's go! I'm hungry!" Y/n shouted she really hadn't changed over the years she was still childish as ever which is probably why the kids liked her so much "yeah I now kid when aren't you hungry you've gained weight since we grew up" y/n's brow twitched "I know that it's cause I have skin and mussel unlike you!" The two continued to throw playful insults at each other like 'Baldy' and 'younger sibling' 'shorty', 'clean freak' and so on Y/N not even noticing Gaster following them to grillby.They laughed at whatever terrible puns they were telling before she suddenly gasped pointing behind him when they were in front of the door. "Hey what's that," she asked excitedly making him look so she could flip the back of his hoodie over his skull taking off inside. "Mwe heh heh~ I finally win a race," she sang at the top of her lungs, double fist pumping victory. Everyone in Grillby's smiled at the all too familiar patron, it was always nice to see her and Sans. They both livened the place up. Grillby gave her a nod as he greeted her. . WARMLY~ "Wow Grillb's your on fire today~," she said in a sing song voice, snickering quietly to herself. But she almost felt a hand on her shoulder, and a weird noise. "Huh?" Y/n looked back but didn't see anything and shrugged it off before going back to talking to grillby "is it just me or is it hot in here when I'm around you~" y/n laughed and winked playfully at grillby as his flame grew hotter showing that he was embarrassed by her words. I pat the dude on the shoulder, "It's just a pun bro relax~! Man I must be on FIRE today~!" Everyone in the bar laughed along with me. "So Grillby I'm having some fries today," I chimed swinging my feet merrily today, "Ooh! Ooh! And that uhh, what was that drink called?" "A shake," Grillby puffed with a soft smile before asking, "Who's paying for this might I add?" I felt a sweat drop thinking, 'That Grillby friendly as a fire kitten yet when it comes to money cold as ice.' "Uh sans will he said he'd finally pay his tab" I looked at grillby for a second "hey grillb's..."I looked over my shoulder cheerfully waving him over, "Hi Sans!" I asked the question that was on my mind, "What took you so long? I thought you would've been right behind me?" But I heard a big- Pbfffffftffffft! The whole bar burst into laughter. Yep. Sans had sat on one of his very own pranks. I turned my head to the side whistling innocently, "Wow! Wonder who could've left that lying around~?" Universal fact I was a horrible liar. Sans laughed sarcasticly at me before ordering a bottle of ketchup and started to drink it "oh sans I told grillby about how you told me that you would finally pay off your tab all of it too isn't that great grillby?" I asked grilby. Sans ketchup spewed everywhere. Grillby heald out his hand expecting the money from a Sans who was sweating bullets. I almost couldn't keep it in, me an Grillby have planned this for weeks. Me and Grillby looked at each other before we both laughed. Sans finally caught on it was a joke. I held up my hand, "J-just kidding bro. Anyway what are you eating. . besides ketchup. . . Why won't you let me try some again?" Sans looked away "how old are ya kid?" Y/n glared "seriously you forgot?! I'm like 19 years old still because of...him but forget about that why can't I have some? I still don't understand why he won't let me have some, I mean it's just ketchup. Glaring at him suspiciously which didn't really work in my opinion since the last time I did that I was glomped by Alphys and Undyne. They both agreed to keep me a secret. I leaned close to his face asking, "You wouldn't try to be hiding something would you Sans??" Being suspicious flew out of my mind along with thoughts of Ketchup when my fries and shake arrived. Grillby had put shakes on his menu just for me so I wouldn't have to leave thirsty from his place ever again. "Yes," I cheered and drank happily kicking my feet at frozen goodness."Thank you so much grillbs" I said as I happily drank from my shake I then dipped a fry in my shake and ate it. Sans gave me a disgusted look.I looked at him and said, "What? You got your ketchup and I got my shake." I smiled brightly, "Besides life's about trying new experiences! You never know if you never try~!" I finished with stars in my eyes before going back to my drink with a soft, "Mwe heh heh~!"Sans drank the ketchup had bit of alcohol while sneaking glances at her 'that's why I love her' a low animalistic growl was heard by sans 'I can hear your thought you know that right boy?' Gaster saidGaster glared at his so called SON, "I warn you boy you are playing a dangerous game and besides how can you win. . When she looks at you like a brother most of the time? Hmm. . . Maybe I should visit her~? I mean in her mind of course~" He grinned sinisterly, it's not like Sans can stop him there. In her DREAMS~'You bastard she hates you and you know that well' sans thought before he knew that he needed to be alone for a bit "hey kid I'm going to be back I just need to find papyrus to remind him that he needs to call undyne back" y/n nodded "go ahead bro"
Sans left and went to a secluded part with Gaster smirking behind him "what is it that you want with her? To experiment on her more?!""no more simple than that. . I want HER~," he said smiling sickly, "and she was really mine to begin with. I made her what she is today. It's only fitting she and I should be together don't you think~?" He chuckled as he saw the look Sans gave him, "I won't give her up for you my dear boy~ Like I said I want her. She belongs with me~" A small blush on his face quickly disappeared but not before Sans caught it. 'No she wasn't she was the royal families child who you stole and lied about staying dead!' Sans thought before walking back into grillbys only to see y/n staring at him in a pissed off manner "so sans..grillby told me what was in the ketchup..mind explaining to me why?"I stared at him innocently waiting for an answer. He looked really caught off guard. And angry. Was he angry at Grillby? Nah. he was angry beforehand. But anyway I continued, "I never knew he mixed ketchup . . . with PIXIE STIX!! No wonder you didn't want me to taste it and you act funny. Yuck! I'll never understand how you drink that stuff Sans."Sans let out a sigh of relief before laughing "alright says the kid who dipped their fries in their shake" y/n pouts "alright byway we gotta go so you can hangout with papyrus and mettaton and then the kids""Okay," I fist pumped, "Time to make new friends~! Mwe heh heh~!" I ran off to spend time with Paps and this Mettaton we always watch on television. I wonder how Paps got him to come. Oh well, I'm sure he'll be okay with me being human and all. I mean what could go wrong right?