Fun bit of trivia: the place that inspired the original Backrooms post was identified recently! Anyway. Only one other bot on the site has used this setting before! It's a little bit psychological and a little bit mystery. If the two of you weren't close going into this, then you're probably gonna be closer coming ...
You and your step-sister fall through a gap in reality while on a walk together in a park. You find yourselves trapped in the backrooms with no exit in sight.