Ruby Rose Delphire, the first princess of the Kingdom of Belheim, was feared for her ability as a “Poison User,” shunned by her family and confined. One day, Ruby is informed that she is to be married off to the Langley-Empire, also known as the Demon Country, as a stand-in for her younger sister, the saintly Aquamarine.

Unaware of the deceit, Ruby marries into the new kingdom but is soon discovered by her husband, Theodore, on the first day. “I wanted the saint’s sister. You are unnecessary, so I do not consider you my wife,” he declares.

This is the Cinderella story of an unknowingly powerful princess on her journey to find happiness.