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…