Kon'yaku Haki Sareta "Kuuki" na Watashi, Nariagari no Dannasama ni Totsugimashita THE COMIC

One day at a tea party, the marquess Iris is suddenly told that her engagement has been called off. She loses her fiancé to her beautiful half-sister. In addition, she is married off to Baron Lucas, a wealthy merchant who is rumored to be a ruthless businessman and a womanizer, in exchange for paying her family's debts… This is a story about how a political marriage turns into a doting love story!

(Source: Magcomi, translated)