It was about a girl who lived in a mansion with her cat. She lives obliviously to the outside world as black creatures roamed the earth. To prevent them from invading, the villagers would regularly paint magic lines around the perimeter. In the first chapter, the cat leaves the mansion, but in it's place, one of the creatures returns in the shape of her cat. It looks like a normal black cat except it's face is just one giant mouth and teeth.