Long ago, in an era when people still used magic and humans and demons coexisted, a Demon King appeared from beneath the earth and disturbed the peace of the world.

"I shall take the princess of the human world! If you want her back, surrender all control of this world to the demons!"

At those words, the whole country was filled with anger and sorrow... and they worried for the princess. In the castle where the demons lived, the princess was supposed to cry, despair, and call for help... but the princess kidnapped to the Demon Castle had a different concern. That concern touched upon the very essence of human needs, and things like plotting an escape or worrying about the citizens she left behind were already trivial matters...

"Ah... I just want to know how to sleep more comfortably."