Saving the Villain Who Was Abandoned by the Female Lead

Story:

The Korean woman is transformed in the novel into a young girl on the verge of death, but fortunately, she was saved by a future villain. She began to work for him, because the villain from the novel "Duke of Perse" was in her mind a fantastic employer. He paid in full and on time. On top of that, this job was easy to do, compared to the work she was used to doing. She knows that the bride of the villain (the heroine of the original novel) cheated on him with the emperor. The bride decides to poison him in order to marry her lover. She knows that as soon as it happens, all who was hired by the Duke, will be killed. Now she has to avoid this fate somehow.