Eris no Seihai

エリスの聖杯

Betrayed by her fiancé’s lover and sentenced to public execution, Constance Grail, a plain viscount’s daughter known for her honesty, faces death—until a mysterious voice offers salvation. Scarlett Castiel, a noblewoman long thought dead, may be her only hope. Together, these unlikely allies uncover a dark conspiracy lurking in the heart of high society, where betrayal, secrets, and power collide.

(Source: Crunchyroll)