The Dark History of the Reincarnated Villainess S01E08 - "Original" Is a Magical Set of Letters

Duchess Amaryllis is Bloody Rosa, the person who has been kidnapping beautiful girls. In order to save Menoa, Iana convinces Cheneau to help her, and they commence working together. But a trap sends Iana and Cheneau tumbling into Duchess Amaryllis' hands. The two are held captive in the basement—an insane "paradise" where the kidnapped Menoa and Cheneau's younger sister are also being held.