Raubritter*

Three years ago, Karamura Neneko's father died. Since then, she's been living together with her older sister, Nanako. They've been living together happily until recently, when Nanako starts acting strangely. There will be nights that she doesn't sleep at home, and then one day she completely disappears. Not only that, but she quit her job at a company that she had been at for a long time.