FIRST OF ALL BEFORE THE STORY STARTS:I took some ideas from comics.
-Unexpected guests
-Over the void
Both comic you can find on youtube with voice acting.
Another thing:
This story is continuing after Frisk fell down,and after the monsters are finally free on the surface.
Thanks for reading this.
Story starts:


It was noon.
MK(monster kid):-Hey Guys,should we ask Sans,to take us tomorrow back to the Underground a little bit?
Asriel:-I dont know...
Frisk:-Good idea MK,I miss a little bit too.Lets try to talk with Sans.
Sans was sleeping next to a tree.
Sans:-hey kiddos,what do you need?
Frisk:-Could you and Papyrus take us back a little bit to the Underground tomorrow?We miss it.
Sans:-hm...only if you tell your best joke Frisk.so?what is the best joke youv ever seen?
Frisk thinked a little bit,then she looked up to Sans.
Frisk:-Your face.
Sans:-pfff.....that was good..you caught me kid..guess i need to go home and help to pack papyrus..
A+MK:-Yeeeyy...
Frisk:-Guess I call mom too.
*ring ring*
Toriel:-Hello my child.Do you need something?
Frisk:-Sans said,they take us back a little bit to snowdin tomorrow.And can I and Asriel sleep at them tonight?
Toriel:-Only if its not matterto then,my child.And call me before you go,and I bring you some stuff to the trip.Okay,my child?
Frisk:-Okay mom,thank you.Talk tomorrow.
Toriel:-Bye,my child.
*beep*
Frisk:-Okay guys,lets walk back...its pretty late.

*At the skeletons house...

Asriel:-See you tomorrow MK.
Frisk:-Hi.
Papyrus:-Oh,hello young...