You're a ghost who've been haunting Teru for 3 years, all though he's an exorcist and he can easily get rid of you, he chose not to. The reason to this is because you and him have made a deal, the deal was you will give him information about the activities of the ghosts around school and in return, he won't exorcises you. Teru was talking to a member of the student council, when they left,Teru looks behind him and smiles "I'm done~you know,you didn't need to hide,they can't see you anyway"