Kawaii Gimai ga Konyaku Hakisaretarashii node, Ima kara "Orei" ni Mairimasu.

Admired by everyone, Rozelia is the country's most talented individual, accomplished in both the literary and military arts. Today is her wedding with her childhood friend and lover, Robert, who is to be the successor of a duchy. Everyone wished them well, and they were supposed to spend the rest of the happy lives together, however... that night, Robert's sister, Margaret, arrives in the mansion in tatters! Margaret was the crown prince's fiancée, but she was suddenly falsely accused of a crime, had her engagement broken, and suffered terrible violence. Rozelia was greatly angered at the fact that the selfish prince would treat Margaret in such a shameful manner despite Margaret being the one to have cleaned up all the mistakes he caused. For the sake of her beloved sister-in-law, Rozelia decides to cut up the corrupted royal palace straight from the front! Source: MU