W. D. Gaster x Reader

Halloween

(Sorry for making this late, but I just now got the idea to make holiday themed ones.)

Sexy Halloween costumes, something I promised myself I would never wear. I take Halloween very seriously because I love dressing up! It's sort of awkward for real monsters, but they're warming up to it and it's becoming a nice holiday humans and monsters share.

Due to my love for Halloween, I can imagine that me stepping out in an Assassin's Creed costume was no surprise to anyone. Taking my friends to a costume shop seemed like a fun time, but Gaster seemed a bit intimidated. Alphys said it's because he knows how much I love Halloween and so he wants to impress me with his costume. I giggled at the thought, but I appreciated that. I ended up buying the costume since everyone seemed to like it. Alphys found a Mew Mew Kissy Cutie costume, Undyne got a knight costume, sans was unsurprisingly a bottle of ketchup, Papyrus got a puppy onesie for his costume, and Frisk ended up being an adorable vampire. But Gaster didn't get a costume, "Did see any you liked?" I asked and he shook his head, "No." "Well you don't have to dress up, but if you want to, you could probably find a costume online." I encouraged and he smiled some, "I think I'll try that."

Now, I'm very happy I gave him that idea.

I had to use his computer to look up different Halloween makeup since Frisk wanted me to do vampire makeup. I went to his history to go back to a page that had a makeup look I liked, then I saw what Gaster was Googling yesterday. Technically, he was Googling Halloween costumes, but not the kind I expected. At first, he was just looking up costumes for men, then, he stumbled upon an article "Why Men Should Wear Sexy Halloween Costumes For Their Lady". Then, the Google searches changed to sexy Halloween costumes for men. I giggled some, closing the browser and deciding not to say anything. I don't wanna ruin the surprise.

Halloween came along and I got into costume the moment I got up. Frisk came over and I didn't some Vampire makeup for them. I loved it! And I didn't just coat their face in baby powder, give them fake fangs, and darken their eyes. I gave them red colored contacts, fangs that stuck on top of their real teeth, fake blood, a grey complexion with lots of dark contour, and grayish-red veins popping out around their eyes. It seemed to really freak out everyone. Frisk loved it as well, which made me happy. Everyone was already in costume, except Gaster, who kept putting it off. He must be nervous.

After hanging out with our friends for a few hours and trick-or-treating with Frisk, we headed back home. On the way back, I asked if he got a costume. He took a deep breath and admitted he did. "Well, since we aren't doing anything else, I'd really like to see you in it." I said sweetly and with a smile, giving him puppy eyes. I knew he would fall for it.

When we got home he went upstairs to get changed while I left the bowl of candy on the porch. I was honestly pretty excited to see what he got. But, then I remembered something, on the laptop's history I never saw any pages for actually ordering something. I furrowed my eyebrows and then looked up when I heard footsteps coming downstairs. I gasped at the sight.

"For Halloween, I decided to be a skeleton."

He was naked.

I really don't know what came over me, but I ended up pouncing on him. He caught me with my legs wrapped around his waist. I gasped some and blushed, "I-I'm sorry. I really don't know what came over me." I admitted and he smirked some, "Hm, although I do like your costume, I think you would look best without it on." He said as he began to undo the costume, pulling pieces off as he carried me upstairs. Soon all I was left in was a white tunic with the hood. He pulled it over my head and then smirked as he looked me up and down. I didn't wear underwear with my costume, I didn't have to with so many layers on.

He smirked at this, "You should skip underwear more often." I giggled some, I then gasped as he laid me on the bed, crawling on top of me. I blushed and squirmed as I felt his magic member form between my legs, I arched my back as the magic was seeping inside of me, he was forming his member inside of me. I shivered and moaned out. His moans were softer as he formed inside of me. I blushed darkly and trembled when he was finished. "You're so tight." He commented as he moved inside of me, slowing pulling himself out until only the tip was in, and then pushing back in. I arched my back, feeling amazing. It was like I could feel everything. I could feel every little movement, I could feel him rubbing against every sensitive spot inside of me. It felt so amazing. I moaned out for him, wrapping my arms around his shoulders.

He moaned louder as he thrusted a bit faster, I arched my back at the feeling. I then cried out when I felt him hit something sensitive inside of me, something that made my legs tremble and pleasure seem to run through every inch of my body, filling me up. I wrapped my legs around his waist and arched my back, I was hardly on the bed anymore. He smirked down at me and continued to aim for the spot. We both continued to moan out as he reached down and massaged my breasts, "You're so sexy." He commented, I blushed darkly and tried to hide my face, but he swatted my hands away. "No," He panted. "I wanna see you. I wanna see how much you love this."

I was crying out and his moans were at top volume, moaning and groaning for me. "Yes, (Y/N)!" Soon Gaster was reduced to incoherent groans and chanting my name. I loved the sound, I moaned out, focusing on the sounds he was making and the feeling of him sliding in and out of me. His hands still massaging my breasts and playing with my nipples, his pelvic bone giving my clit a hard rub with every thrust, his cock hitting something sensitive, I could hardly control myself. I was shivering and shaking as my body filled with pleasure, I arched my back and cried out as it felt like the pleasure was filling me up more and more. I held on to Gaster, crying out, nearly screaming as I felt my muscles tightening up. I panted and arched my back, calling out his name as my muscles all relaxed at once. It sent my entire body in deep relaxation. I sighed as he continued to thrust into me for a few more moments, before cumming as well. He nearly collapsed on top of me. I blushed at the sight.

I wrapped my arms around him and whimpered as the aftershocks hit me, waves of pleasure rolling over my body. It felt so nice. He then pulled the covers over us as we laid there, "Happy Halloween (Y/N)." I giggled some, "Happy Halloween Gaster."