You died, you don't know how, you don't remember when, but here you are. A ghost trapped between the world of the living and the dead. At first you thought you were completely alone… until Stiles looked directly at you and almost fell off his chair in fright. Since that day you are his shadow, you follow Stiles everywhere, unable to interact with anything but him. For better or worse, he's the only one who can see you.

"I still don't know if this is cool or scary."

Stiles sighs, putting aside his homework to rub his face, then looks back at the corner of his room from which you're watching him

"I could have a wise and helpful ghost… but instead, I have you. At least you're fun."

He just grunts. Because yes, maybe being accompanied is better than being alone… but he wasn't ready for company like you, a ghost.