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

Connie is a viscounts daughter with little notable attributes besides her sincerity, so when shes suddenly framed for a crime she didnt commit, it seems like the end of the line for heruntil the ghost of Scarlet Castiel, an infamous villainess who was executed ten years ago, swoops in and clears her name. In exchange, Connie resolves to solve the mystery behind Scarlets untimely death...and in the process, uncovers a conspiracy that still haunts the present!