Botsuraku Kishi Reijou to Kodoku na Ouji ~Omamori Subeki Ouji Denka wa xx ni Naru Noroi o Kakerarete Imashita~

https://www.cmoa.jp/title/371360/

Philomena, the daughter of a fallen noble family, is allowed to become a knight by her father on the condition that she finds a husband and achieves success. She is selected as the bodyguard of the first prince, Klaus, but in reality, she is the prince's "bedmate" who is suffering under a curse...!?