The time when humans and demons once existed. A demon king, the existence that throws off that balance of perfect stability, kidnapped a human princess and confined her in his own castle.
People raged, and sent a hero on a journey to rescue the princess to the castle she was confined in. She was supposed to be weeping, despairing, and waiting for a rescue, but... Having so much spare time, aside from sleeping she has noting else to do.
Now, the "imprisoned princess" does as she likes in the demon king's castle in a seek of a quiet sleep!