Undertale Smut

Gaster!Sans x Shy!Half-Monster!Reader

(Another request! Quite a lot of prompts here but I managed to come up with something last night. I decided to add something to make it even better!)

It was odd being a half-skeleton half-human hybrid. You were born in the underground when a human fell, and she managed to have a baby with her boyfriend. You had a happy life.

Now that you are an adult, you had your fair share of problems and responsibilities. You were never really fond of them.

Being alone in your house was actually calming to you. You didn't want help or anything. You just wanted to be alone being the shy person you are.

The thing was, this skeleton kept bothering you because he wanted to collect samples for his brother's research on humans. You were kind of bothered by this because your skeleton side seemed to be more prevalent since your body was a magical shade of (F/C). The only thing that wasn't covered was your head. You had no skin, only magic. He didn't know how he could collect info if you're like this.

But one day, something odd happened.

You felt all heated up all of a sudden. You had all of your fans on, despite it being snowy and cold outside. You were laying on your couch, complaining about your body's heat. It seemed especially hot in your crotch, and you didn't know why. You never touched that spot unless you were showering. You didn't want to, you were shy, and you didn't want anyone to see you.

But your instinct gave you no choice.

You went into your bedroom and pulled down your skirt. You flopped on the bed and looked down. Your crotch was already soaking wet. You sobbed. You couldn't do it.

You were blushing madly. You were dripping, but you just couldn't do it. You didn't want to take any chances of anyone seeing. Then you heard a knock on the door.

You were filled with dread as you squealed a little bit. You didn't want to answer the door. It was probably Sans, asking to collect samples again.

You couldn't open the door. You put your skirt back on. If he walked in, he would see you panting heavily along with being panicked.

And then, the door opened with a loud creak.

You heard him walking up the stairs. You decided to hide under the sheets. But when he came in, he found your hiding spot.

"Why are you hiding?" He asked. You shuddered and didn't say anything. "Come on, you can tell me." You sobbed a little bit and decided to answer. "I'm all hot, especially in my crotch, and I don't want to get rid of it because I don't want to do what I think I have to do..." You were explaining everything so fast that Sans couldn't even understand. "Slow down, I know what to do."

"So do I!" You objected. You blushed madly. Him helping you would make things even worse. "Then why don't I help you?" He grabbed you from under the sheets, put you onto the bed, and pinned you down. You were so scared. You didn't want to do this.

He pulled down your skirt to expose your ecto-vagina. Sans licked his teeth with his magic tongue and bent over. You whimpered as his breath puffed against your entrance, making you squirm.

"Hold still." He said before you gave in. His tongue slithered out of his mouth as he licked your entrance at a slow pace. You yelped, but you didn't know it would feel so good.

He circled his tongue around you clit as he pumped a finger into your entrance. He stopped licking you and looked up, a bit of your liquid hanging off of his tongue. He kept pumping his fingers into you.

"You taste so good..." Sans complimented. You covered your face with your hands as he leaned back down and started pumping faster, teasing your clit with his yellow tongue.

You let out a muffled moan as he went even faster. Tension was building up in your crotch as the heat rushed into your crotch. You were getting even hotter. It was unbearable.

You let out a loud moan as you released. Sans finally pulled his fingers out. You were still so hot, signaling that you weren't done yet.

"There's still one more step." Sans pulled down his pants to reveal his magic dick. You closed your eyes. You were too shy and you didn't want to see it. "Don't worry, (Y/N), you're fine." He rubbed his member against your entrance. He finally thrust into you. He was slow to start.

The feeling of being filled was overwhelming. It hurt, but it felt good at the same time. Sans pulled up your shirt to reveal your magic breasts. He bent down and licked one of the nipples. It all felt so good that you couldn't help but release.

In the midst of all of the action, Sans gave you muffled praises that were inaudible. You knew he was so close. He was grunting and moaning loudly.

You screamed his name as you finally came one last time. It didn't take long until he reached his climax.

"Ohh... (Y/N), I'm cumming, ah, NNGH!" His cum finally covered your inner walls. Sans pulled out and rubbed your cheekbone. "You did great..." He praised you as he fell asleep. It didn't take long until you fell asleep as well.