The Holy Grail of Eris, Vol. 1 (manga)

The Grail family lives by the principle of sincerity. When meek Constance Grail is framed for theft, she quickly loses her fiancé and her reputation. As she navigates the treacherous landscape of high society, she encounters a woman who bears an uncanny resemblance to the deceased Scarlett Castiel. This discovery raises questions about Scarlett’s dark past and Constance's own future. Constance must untangle the web of deceit that surrounds her while grappling with her own sense of identity and morality in a world where sincerity may not be enough.