Yu Eunha is the unfortunate heroine of the erotic BDSM novel The Demon's Vivace, where she endures daily beatings from the male leads. Her miserable existence seems never-ending—until the author suddenly announces an indefinite hiatus. Desperate to keep her story going, Eunha decides to take matters into her own hands: if the male leads won't continue to torment her, she'll make them suffer instead. But when the Demon King, who's supposed to be her cruel master, refuses to harm her, Eunha flips the script and embarks on a mission to train him into the perfect sadistic lord. Can she turn this reluctant villain into the ruthless master she needs, or will her twisted plan backfire spectacularly?