The Holy Grail of ErisEris no Seihai,エリスの聖杯

Connie, the daughter to a Viscount whose only value is her honesty, and Scarlet Castiel, the most reviled villainess of the era who was sentenced to death ten years ago. When the two people who were never supposed to meet encountered one another at a night party, the story that should have ended with Scarlet’s death began anew. Although their relationship only began out of mutual interest, they soon became true partners in an effort to unravel the mysteries of a grand conspiracy borne out of the past, that still has a vicious grip on the present.