Another Universe (underfell and undertale sans x frisk)

This is my first story! So uhm...yea!
It will include underfell sans and undertale sans!
It will take place in underfell, with no other characters from undertale except for sans and frisk
Frisk is gonna be a girl in this version and her age is old
ages are:
sans: 17
frisk:16
sooooooooooooooooooooooooooooooooo yea
no lemons are gonna be here.