Sans x Frisk

Frisk falls down into the underground not knowing what will happen. She meets toriel, who tells her a way she can get out... Back to the human world. She go's on a journey, meeting many different monsters. One in particular catches her eye. A skeleton named sans.
Sans is a jokester and a prankster who has always lived in the underground with his little brother, papyrus. Sans has always been lazy and messed with his brother. But when he meets a human, frisk, he catches feelings for her instantly. But when he finds out she is trying to go back to the human world, he tries everything to keep her in the underground.