The Holy Grail of Eris - S01

Constance Grail is the only child of the well-known Grail family, whose motto is "Be you sincere," and at 16 she is the living embodiment of that motto. Constance gets engaged to help her father pay off his debts, even though she had always hoped to marry for love. Still, she resolves to go through with the marriage for the good of the family. During a ball hosted by a fellow noble, Constance meets a mysterious, alluring woman lingering at the edges of the room. She urges the woman to come into the ball before losing sight of her. Not long after, her fiancé's lover confronts her with accusations of theft. Facing the ruin of her reputation, Constance begs for help. In response, she is possessed by the woman she met earlier, who turns out to be the ghost of Scarlett Castiel, a famed villainess. With Scarlett's quick wit and intimidation, Constance is saved, and her engagement is annulled. In return for her help, Scarlett enlists Constance's aid in investigating the events that led to her execution 10 years earlier. Though she was charged with the attempted poisoning of the crown princess, Scarlett claims she never did it. Constance agrees to find the answers, even though her efforts will be watched by the people who once knew Scarlett and might prefer the truth stay buried.