The Half-Breed [UNDERTALE FANFICTION]

Prologue

Sans sat on the edge of the east-flowing river, watching the water flow smoothly. He smiled, looking around. His father told him he'd meet him here, but he was late. He yawned, standing up when he heard footsteps behind him. "Dad?" He asked towards the footsteps, watching the bushes that they were coming from.

Gaster stepped out of the bushes, carefully carrying a small bundle. "Sans, quiet down, I don't want people knowing we're here." He smiled, sitting on the edge of the river and gesturing for Sans to sit next to him. "Sans, you need to promise me you won't tell anyone about what goes on here today, this is important."

Sans smiled, nodding at his father, "of course, dad. What is it? What's that?"

Gaster smiled, moving the bundle slightly to reveal the face of a small, human baby, about 8 months old, "this little one is going to be living with us, now. They'll be staying in the lab, I've already set up accommodations down there."

Sans looked at the child, looking up at his father, "a human? Aren't those illegal?"

His father sighed, watching his son carefully, "that's why you can't tell anyone. Her appearance is human, but she's half monster, the likelihood is she has magic, just like we do. Sans, if you tell anyone, something very bad could happen to her. You need to promise you won't tell anyone, even Papyrus, as I fear he won't be able to keep it private."

Sans nodded, looking at the child, "half monster? How did that happen?"

"A friend of mine was secretly with a human, they died a couple days ago and left the child under my protection," Gaster said solemnly, looking at Sans, "we're going to have to teach her how to use her magic, and we'll have to keep her hidden, at least until the law against humans is lifted, if it ever is."

Sans looked up at him, "we?"

"Yes, Sans. I'll need your help to take care of her, especially while I'm at work."

Sans nodded, looking at the baby again, "can I hold her?"

Gaster smiled, carefully giving the child to Sans. He smiled, rocking her lightly and playing with her. She smiled, cooing and reaching up for his finger.

"Seems like she likes you," Gaster smiled, looking at Sans, "Sans, I need you to promise me something else."

"Yeah, dad?"

"If anything happens to me, you'll protect her, train her, just as I did. She's your little sister, now, after all."

Sans smiled, "sister?" Gaster nodded softly, Sans looking down at the child, "of course, dad."

He nodded, standing up, "we should head back, get her out of sight."

Sans nodded, standing up, careful to keep ahold of the child, "dad?"

"Hmm?"

He looked up at him, "What's her name?"

"Quinta."