Poisoned Chalice: The Poisoned Princess

To take revenge on the husband who betrayed their nation, Adelaide returns from the brink of death. To get revenge on her husband, Adelaide decides to use her innocent brother-in-law, Cadis, and to let him go once her revenge is complete. After all, she was the poison he mistook for the Holy Grail. "The only thing I'm afraid of... is being abandoned by you." (Source: Naver, translated)