Undertale & Deltarune Oneshots

☆Embarrassing- Sansby & Gaster

Plot: When Sans tells Gaster that him and Grillby are dating, Gaster finally becomes a typical father and begins to embarrass Sans

Extra Info: Sans and Grillby are in high school

A/N: Sorry if what I write isn't what a typical father would do. I don't have a dad so I wouldn't know lol, and when I tried to google it all that came up was multiple websites about narcissistic fathers 

Requested By: acethenonbinary01

~☆~

Sans took a deep breath as he held a shaky hand over the doorknob to his house. His boyfriend, Grillby, stood behind him, placing a hand on the skeleton's back for reassurance. They decided that today was the day they would tell their families about their relationship. Grillby's parents were more than supportive and were even happy to agree to let Grillby stay at Sans's house is everything went over well with his father. They knew as well about how bad Sans's anxiety can get even if things go well.

"This is a bad idea," Sans said, about to talk off before Grillby gently grabbed his hand.

"No, it's not. He already accepts you for being bi, I'm sure he'll have no problem with us," Grillby replied, gently pulling Sans back towards the door. With a small smile and another deep breath, Sans opened the door.

They walked in and saw Gaster sitting on the couch with a book in hand. Sans couldn't hear or see Papyrus anywhere, so he assumed that his younger brother was at a friend's house. Gaster looked up from his book when he saw the two enter the house.

"Welcome home, Sans. Hello, Grillby," Gaster greeted, placing the bookmark back between the pages and closing the book. 

"Dad, I um...we uh, w-we have something to tell you," Sans said, his hands shaking in his jacket pockets. Gaster could tell by the slight quiver in Sans's voice that this was serious, so he gave his full attention to the two monsters and motioned for Sans to continue. Sans slowly took his hand out of his pocket and held it out for Grillby to take, which the fire monster happily did. "Grillby and I are dating," Sans finally spit out.

Gaster smiled and stood up, walking over to the two boys and placing a hand on their shoulders. "Thank you for telling me, boys. It's about damn time," Gaster said, chuckling at their shocked faces. "Oh please, you don't take me for a fool, do you? I've been waiting for this confession for months." Sans was so shocked that he didn't know what to say, but he didn't have to, for Gaster knew what it would be. "Yes, Grillby may stay the night, and yes I don't care if you sleep in the same room. Just use protection and I don't want to hear a bed creak," he said before walking back over to the couch and picking his book back up.

"D-Dad! Not funny!" Sans said, his face a bright blue and Grillby's face a bright purple. 

"Oh, so only you can make jokes in this house. Just go on and get Grillby settled, I'm going to make dinner in a little bit," Gaster said, smiling as he put his book back on the shelf and heading into the kitchen.

Sans rubbed the back of his neck and looked over at Grillby, "Sorry 'bout that, Grillbz."

"I-It's fine. It's a dad thing I suppose. My dad gave me a thumbs up when we left my house," Grillby responded.  The two said nothing after that, just making their way up the stairs and into Sans's room to hang out.

Gaster remained downstairs. Dinner was almost ready, and while he let the last bit of it cook for a little longer, he thought of all the ways he could embarrass Sans this evening. He had been waiting for the day when he found something to embarrass his sons over. The day where he could be a stereotypical father was now.

After a little while, Gaster finally called the boys down for dinner. They seemed better than they were before, considering that they came down the stairs laughing over something Sans had said. Once they filled their plates and sat down at the table, Gaster instantly attempted to make conversation. 

"So how long have you two been together?" He asked, not getting as big of reaction as he expected based on the previous interaction.

"About four months, right Grillbz?" Sans responded. He was always bad at remembering things like that, but he was trying his best.

"Yeah, good job, Sans," Grillby said.

"If you struggle to remember dates, you'll probably give me the wrong one to your wedding," Gaster said, a small chuckle following. Both monsters instantly blushed fiercely, Grillby placing a hand over his face and looking away while Sans slammed his skull onto the table. Gaster erupted into laughter, placing his hand on Sans's skull. "You are so easily flustered, son." 

"Because it's day one of you knowing and I already regret it," Sans replied, his voice muffled by the table.

"Alright, alright, I'll stop," Gaster said, allowing his son a bit of mercy to at least get through dinner. They talked about regular stuff after that. The end of the school year slowly approaching, how Gaster was doing at work, Grillby helping out more with his parents' restaurant. It was nice. 

Once dinner was finished, Gaster watched as the two boys cleaned their dishes at the sink together, just laughing a talking. That was when he knew they truly were meant for each other. Grillby completed Sans, he was one of the few people who could handle the boy and seeing them being so domestic already was the cherry on top.

They decided to turn in for the night after that. Sans and Grillby got ready for bed while Gaster grabbed his notebook to look over some work that he needed to get done tomorrow. Sans looked over the railing from upstairs, Grillby standing next to him.

"Night, Dad!" Sans said, turning around once Gaster said it back. But just before Sans made it to his bedroom, Gaster called out to him one last time.

"Oh, and boys! I'm serious about protection!" He said with a small chuckle.

"Dad, seriously?!" Sans said, harshly shutting his bedroom door, ready for that to be his final resting place from the embarrassment. Though he supposed that it was typical for Gaster to do that, and it was nice seeing him not so serious for once. 

The two monsters crawled into bed and faced each other, smiling. Grillby's flames illuminated the room a small bit, so both of them could clearly see a small blush on either of their cheeks.

"I think he took the news well," Grillby said with a chuckle.

"Don't you start too," Sans responded, pulling the covers up to his shoulders and cuddling up to Grillby's chest. "Night Grillbz."

"Goodnight, Sans."