The Holy Grail of Eris

The Grail family has a single guiding principle in their lives—Thou Shalt Be Sincere. However, sincerity alone can only get a lady so far in the twisted world of high society...as meek Constance Grail soon learns after she is framed for petty theft and loses her fiancé and reputation in a matter of minutes. But one gaze on her isn’t quite as chilling as the others, though the woman’s uncanny resemblance to Scarlett Castiel must be a coincidence. After all, Scarlett isn’t just extremely wicked…she’s also very much dead. 

(Source: Yen Press)

Constance Grail, known as Connie, is a plain and ordinary Viscount's daughter, and Scarlet Castiel, the daughter of a duke who was once executed as an unparalleled villain. Connie is saved from a difficult situation by Scarlet's ghost, but in exchange, she must continue to accompany her on her quest for revenge. 

Due to certain circumstances, Connie and her friends end up visiting Elsor, the homeland of Scarlet's late mother. According to Scarlett, this is where "the Star Crown of the Faris Empire's last princess rests." 

(Source: Drecom, translated)