[Luckily she doesn't notice it, so she can't be bothered to ask.]

The souls of then dead, in this case. I died back home [Don't ask how.] and became one...although ghosts where I'm from are very different than most...I think.

[Who knows with all these weird worlds and whatnot.]

Becoming one, I was able to maintain my position in the school just the same as how I did alive, except I had a certain...edge over the more unruly students. I believe you could call it...pheromones?