Sayounara, Watashi no Reiguu Seikatsu - Party de Koe wo Kakete Kita no ga Yabai Otoko Datta Ken

Leticia finds herself ostracized after her father takes a mistress. For the sake of her mother, who suffers from a chronic illness, and for the sake of her own future, she makes a firm resolution! "I'll definitely find a husband! ...Even if I'm a second wife or a fifth wife..." However, the men she associates with end up ruined or arrested... And then, for some reason, she gets involved with the son of Marquis Brennan Macbeth, a notorious playboy—!? (Source : Riberion, translated)