Basically Sans is the slave I know you guys know what I mean when I say 'slave' and Pap is the master now continue)
(Sans POV)
I was making food for my master and I felt a hand hold my waist and one go up my leg. I smacked the person behind me but I saw it was him "Oh my god Master I'm sorry!" He got up and smiled "YOU REALLY KNOW HOW TO HIT A PERSON." He grabbed my waist again and pulled me close I blushed and he kissed me I kissed back immediately and he slipped his tongue in exploring every inch of my mouth the feeling was amazing and I moaned a bit. He smirked and pulled back "Why did you stop?" I asked and he bit my neck I couldn't help but moan louder "Ngh Pap~!" He licked up and down and I gripped his shirt "GOD SANS YOU'RE SO HOT~" I blushed and he picked me up and brought me to the couch he pinned me down and started dry humping me I moaned loudly in pleasure "Papyrus!~"
(Papyrus POV)
I felt my erection grow and I took off his outfit then my own. I thrusted into him hard making him scream my name I nibbled his neck bones and pulled out then slammed back into him making him go crazy. I smirked and kept thrusting into him at a fast pace soon he was gonna cum "I'm ahh~ cl-close!~" I thrusted faster and faster then he came I wasn't at my climax so I switched the position and thrusted into him deeper that way he moaned more "Ngh~ A-ahh!~" I rubbed his spine and smirked his moans getting louder and I soon hit my climax and came he did too for the second time. I kissed his head "I LOVE YOU SANS~" I said and pulled out laying him down with me on top "Love you too Pap." Sans said then drifted off to sleep "I'LL MAKE SURE NOBODY ELSE CAN HAVE YOU~" I smiled and went to sleep too

...

...

...

"NOT EVEN YOU FANGIRLS."