Kalheinz Stories

One day, a normal girl was abducted by a cult, masquerading as a lab. A year later, she escaped, but when she was about to be caught, a demon saved her and offered her power in exchange for something; she needed to "do a few tasks" in a mansion far away. Without any more instruction, she is sent to the mansion. Why is this demon sending her here? What possible reason does he have for all of this? A/N I haven't played the games. I've only seen the anime and I've read Karlhienz's backstory and goals, so I'm going off of those.