Ghost World/WMG

Enid was Dead All Along.
She had comitted suicide and was haunting the town as a ghost. The mysterious tagger is trying to inform her of this. The events of the story are actually Enid's confused ghost remembering why she decided to kill herself. When she recovers her memory, she realizes the same things that didn't make her town worth living in make it even less worth haunting and she catches the bus to the afterlife.