Zutaboro Reijou wa Ane no Moto Konyakusha ni Dekiai sareru (Betrothed To My Sisters Ex)

Marie has spent her life living under her sister's shadow as the two grew up in an impoverished baron's home. Every nice thing went to Marie's sister, leaving her without even a proper dress! And right when her sister was being married off to a wealthy Earl–tragedy strikes and Marie's sister is killed en route. With the dowry already spent, it's decided that Marie will take her sister's place and become the Earl's betrothed. But, when she gets there, she finds there's been a serious mix-up—the proposal was a total misunderstanding! Can Marie win the heart of the handsome Earl, or is she destined to live a life without a single nice thing?

(Source: Seven Seas Entertainment)