Why tf are demons from Demon Slayer here?! (On Hold)

You were kinda just chillin at with your two best friends when demons from Demon Slayer kinda just appeared. So now u gotta deal with that. Manga spoilers so be aware of that. Lots of swearing too. I don't own Demon Slayer as you know, I only own Mariana, Zaria, and Y/n. ITZ A JOKE BOOK IT AIN'T MEANT TO BE ALL SERIO...