Outaishi Denka wa Koukyuu ni Uranaishi wo Goshomou desu

A duchess with fortune-telling abilities is forced into a high-stakes investigation when the prince's advisors threaten her with prison unless she uncovers which of three princesses plotted the murder of the queen and prince. Desperate to avoid a grim fate, she delves into the treacherous secrets hidden within the palace's inner sanctum.