Undertale Smut

Gaster x Reader

(This was requested by @GasterJr. He also requested an Asriel x Reader so I'll do that next. Just an FYI, I haven't been adding fanfictions recently because of summer school and it being hot as balls here in California.)

The monster and human war had finally ended, and the monsters came up to live with the humans in peace. Everything was going well and everyone got along thankfully. You weren't completely used to it yet, but you made a few monster friends.

After the monsters came to the surface, everyone had been talking about this one monster that rarely came out and was hiding from the humans, even after coming up to the surface. He was either shy or didn't like the humans as much. Nobody really knew his name, but all they knew is that he didn't speak English.

Curiosity sparked inside of you and you decided to set off and find this monster. You never told your friends that you were leaving, which was dangerous, but you wanted to see him for yourself. You were off before you know it. Hopefully he wasn't too far.

After a few hours of wandering you came across an empty alleyway. You could've sworn you saw a figure at the end, but he vanished within a few seconds. You walked down the alleyway, despite there being nothing there again. Hopefully this figure would show up. You had a suspicion that this was the monster that everyone was talking about.

Suddenly, the monster reappeared, this time facing you. His face was white, unlike the rest of his body, which was pure black, except for his hands. He had empty, black eye sockets with black lines trailing from his left eye to his mouth and a line trailing from his right eye up to the top of his head. His hands were white with two holes in between them, which was an odd feature to you.

"Hello," you said to the weird monster. Before you could finish your sentence, he cut you off. He spoke an odd language that you couldn't understand. He approached you, making your gulp. You didn't like the looks of this.

Before you knew it, he was right up to you, his hands caressing your sides. It felt really weird, but oddly... pleasing. You panted a little bit. You thought this was what you wanted. He slowly dragged his hands down to the top of your pants, slowly pulling them off. "What are you doing?" You gasped. You didn't want to do this here, even if there was nobody around.

He slowly slid a hand down and rubbed your clit with his finger. You couldn't help but let out a quiet moan. You didn't know what was going on, but you knew what was going to happen.

The monster pushed you backwards so you laid onto your back. He spread your legs open and moved his now visible tentacle cock inside of you, already thrusting at a slow pace.

You could feel his cock wriggling inside of you, which made you completely mindless in pleasure despite the slow speed he was starting with. He slowly went faster, his cock starting to wriggle at a faster pace as well. You closed your eyes and moaned as loud as you could. This was just too much for you to handle.

The monster let out a few audible moans himself and starting praising you in his language that you didn't speak. He got to the point where his cock was pulsing inside of you, making you cum.

Your walls tightened around the monster's cock, which was enough to make him splatter his seed all inside of you. You panted heavily as he pulled out of you.

You never knew that this would happen, but you did get a good time out of it.