Munou to Sagesumareta Reijou wa Konyaku Hakisare, Henkyou no Seijo to Yobareru: Gouman na Konyakusha wo Sute, Goei Kishi to Shiawase ni Narimasu

Emeline is the only direct descendant of the Margrave of Garrett, whose powerful magic protects the boundary between the monster and human worlds. However, for some reason, she lacks magical powers. Because of this, it is her duty to marry Damien, who possesses strong magical powers, and have children with him. However, Damien is a man who constantly threatens to break off their engagement and belittles Emeline. Her only emotional support is Emeline's personal bodyguard, Bart, and her maid, Alma. Bart secretly has feelings for Emeline, who continues to endure unreasonable treatment out of a sense of responsibility. Even if their feelings are reciprocated, the two are in a relationship that can never be together! A love fantasy about broken engagements and differences in social status!

(Source: Young Champion Web, translated)