Gambangeseo Namjajuingongeul Mannatseumnida

A person wakes up in a prison, having been reincarnated into a 19+ romance novel as the villain's younger sister. They are imprisoned at Kambrakam for their brother's crimes. Also in the prison is Henrich Doran von Hel, known for a curse that causes him to transform into a beast. In the original story, he was meant to meet the female lead and share a night with her there, but the events have changed due to the protagonist's presence. The future remains uncertain as they become entangled between the novel's main villain and its male lead.