Chuu Boss Reijou wa, Taijou-go no Jinsei wo Ouka suru (Yotei).

One day she wakes up to find that she, Reimika, who was supposed to be an ordinary office worker, has become Countess Reimi from another world! Apparently, she has swapped places with the despairing Countess Reimi after her marriage to her favourite Squire Baudi is interrupted by the arrogant Marquis' son. What's more, this is the world of an "Otome games", and Reimi is in the delicate position of being the miniboss!
What is this unreasonableness! I'm going to blow away the bad engagement and the fate of being the miniboss, I'm going to blow it all away!
A love fantasy about a young woman who struggles to find happiness!