Yandere Undertale Au's x reader oneshots

fell!sans x shy!reader

Y/n p.o.v
You we're with papyrus in the waterfalls. You've been showing mercy to the underground but...sans act weirdly everytime he saw you but you we're now with papyrus heading to alphys house to watch anime but papyrus told you he wouldn't watch cause he doesn't have interest in anime so you,alphys and undyne only

Sans p.o.v
I was stalking my beloved y/n and with my stupid brat brother even I called him boss such an pain on the butt. I was getting tired and think of something and then I followed y/nand paps to see y/n is the only one come inside the lab 'yes! Here we go' I said smirking and teleport behind boss "sans what are y-" before papyrus finish his words. I use my telekinesis in paps soul and chucked slightly and throw him on the ground hardly so I can broke his bones "s-s-sans what are you doing" paps said as he groan in pain "we'll this is the reward for stealing my beloved y/n and for now on, this time is KILL or BE KILLED if someone stole my y/n" I said and summon some bones behind paps making him yell in pain sending him agony to herself until he became into dust

Y/n p.o.v
I was seating in the couch with undyne and alphys while we we're fangirling in the anime movie (a/n: gosh umm...never mind) until I felt someone watching me or something I then tap alphys shoulder as she hum "yes?! Y/n" alphys ask "may I go the the bathroom?" I ask she nodded as I run straight to the bathroom

Sans p.o.v
'Great now's my second chance' I then got up and walk inside alphys lab and pretend I was hurt and slice on bone part of my body even though it didn't gave me pain so I entered and act like I was dying "s-sans what happen to you!?" Undyne said and quickly rush towards me as I smirk and some bones and launched it on undyne even though I don't have to move my hands,then undyne turn into dust as alphys just stand there and quickly rush on the bathroom, even though I won't let him and grab his soul and kill I'm just I time before y/n would leave the bathroom. After done killing those stupid ass I then take my jacket off since my sweater doesn't even have dusts on it and go tot he couch and act like I was dying until m sweetheart exited the bathroom then saw me bleeding even though it doesn't hurt me

Y/n p.o.v
I walk off the bathroom to saw fell was on the couch bledig on his arm, ive gotten worry d quickly I rushed of sans "s-s-sans yo-you're bleeding" I said in the worriest tone as sans chuckled and kiss me without me knowing that he was gonna do that,fell then pull away from the kiss and whispered to me "I love you,sweetheart" then all black