Imouto ni Konyakusha wo Torarete Kono Tabi Shuuakukou to Oshitsukerarekon suru Hakobi to Narimashita @comic

"First, my little sister steals my fiancé. And now... they want me to marry the most hated man in the kingdom? Oh, what fun this will be." Raised under her father's thumb and treated as an inconvenience her entire life, Lucrezia has survived on one thing alone—delusional optimism. If this is a test of love, then so be it. With a crooked smile, she marches straight into the lair of the so-called Vile Duke. But the man awaiting her isn't the monster the rumors promised. What should've been a miserable ordeal... Becomes a life too sweet to be real?! Two outcasts. One unexpected chance at happiness. A love story where the underdogs rise. (Source: TO Books, translated)