Undertale X Reader

It's Simple Biology (Gaster Lemon)

You sliced a red figure in half as it puffed into red smoke as Gaster blew one away with a blaster "That's all of them." You made your axe disappear "There's been tons more recently..." "We don't know what this could mean the return of...If only I could grab a sample." She rubbed her hair and sighed as you held her shoulder "Let's go inside then, We'll figure the rest out later." She nods as the 2 of you walked off back to Gaster's Room/Lab.

She slowly slipped off her lab coat and hung it up "It's not a big deal. We'll get there in time!" "We might not (Y/N) that's the problem!" You looked at her as you hung your coat on top of her's "We don't know what this could mean and what it could bring! The end of the world might be tomorrow if we're not careful!" You sighed as she scoffed "Oh, You're sighing at me now?" She held her hands on her hips as you turned to face her "It was a sigh of frustration! Because you're worried about possibilities when the possibility may just be another core leak and that's just the radiated souls!" She walked closer "You don't know that!" You got closer as well "Neither do you!" "Do not start with me (Y/N)! I'll fight you if I must!" "Let's fight then!" You 2 began to aggressively kiss each other, Gaster jumped up on you and tried to tackle you down but you instead pinned her to the wall "Mmmm~" She moaned as you used a bit of tongue "Gmmmph~" "Mmmmmphh~"

You 2 continued to make out for a bit longer until you pinned her onto her bed and she used her magic to close the door, She tapped you twice and you pulled back "Sorry...I almost forgot that I need breath..." She let out a long sigh "It's okay...It seems as if your male cells are getting excited." You squinted "Are you going to use all sex words as biological nouns?" She nods with a cute smile as you decided to get up and strip "I might as well remove the sheep fabric I wear so I may fully express my biological pleasure so we may do the connection with the male and female genitalia~" She laid on her side, Hand on her hip and her other hand holding her head up...Fully nude.

You climbed on top of her to continue kissing except you moved down her neck and licked it. Going down lower you licked her chest and gripped her thighs tightly with your hands "Mmm~ Mm- Ahhh~" She laid her head back as you looked up to her "I'm ready...for your insertion." You smirked and moved upwards, Slowly inserting your member while she tried to hold her loud moans in "W-will anyone here us?" She whispered as you brushed her hair back "Not if we're secure about our secret intercourse..." She bit her lip, the thought of secretly doing this without anyone knowing excited her.


You continued to move gently in until it was all in "AAH-...A-aaah..." She whispered while holding your arms "It's okay~ Shhh~" You went down to kiss her lips, Her black lipstick spreading more across your lips as you slowly began the motion. Her legs begun to wrap around you while you moved your hips upwards and then thrusting back down into her. She pulled away from the kiss to let out a gentle "Ooohh~" You went down to lick and nibble her neck while you begun to speed the motion up a bit but that was as fast as you wanted to go. She let out a few gentle as well as loud moans but they weren't loud. 

Your muscles were relaxed, your body felt soft against her soft gentle yet cold dead skin...Her lips were like the pure taste of death...but you couldn't get enough of it, Each thrust felt more pleasurable than the pain. Clearly this was meant to be where you died but this pleasure was enough for her to enjoy it more than enough for you to survive through this enjoyable thrusting in and out...

After a soft gaze into each others eyes you moved faster and finally pulled out to release your semen over her as she tasted it "Mmm~ Tastes lovely, I'll take some of this for science if you don't mind?" "Sure...But I'm here if you need more." The 2 of you shared a kiss.

I know I said I wasn't doing very well but today I felt pretty confident and I thought I should take this opportunity to deliver. Something i didn't get to clear up was that I unpublished this book so the reason most of you got a ton of notifications was because I was re-publishing the whole book. Sorry again and I'll try to get back as soon as I can.