Got stuck in demon slayer multiverse undertale au X demon slayer

in this au Classic know about anime and fandom stuff they are friend with classic and the au didn't know the anime and fandom stuff yet and tomioka are classic little brother and classic in the demon slayer multiverse will became girl and yes i ship sans!au x classic!sans

one day classic was about to go demon slayer multiverse cause he had a mission in the middle of the night classic open the portal what sans didn't know that there was au saw this when classic first enter the au secretly enter the portal and they end up in other world they tired teleport but not used when night time they stay together but then they saw a human they go to the human and the next thing the human stared attack them but someone will help read more to find out!

lemon
angst
fluff
Not good at english :/