How did she get there? No one knew.
She just suddenly appeared.
Y/n couldn't even think of a logical explanation for her to get lost from her time period or suddenly hopped to some ancient universe. But she's here. Trying her best to fit in for a world where demons are the ones plaguing the world and not Ghouls.
All she could do is painstakingly take on a role she doesn't really want in order to hide her identity from everyone else. Meeting a Demon slayer and travelling with them and having encounters with some people who just doesn't wish to leave her alone just like in her old world.