Kokurou Ou to Shirogane no Niehime: Henkyou no Chi de Saiai wo Eru

Princess Edel of Zerth, who grew up being oppressed by the queen and others because she was born to a concubine, is to be married off to the victorious country of Ostrom in place of her half-sister as compensation for losing a war. Her partner is Ortius, nicknamed the "Black Wolf King," a barbarian king rumored to have only the ability to fight with his beast-like body. However, on the day of the wedding ceremony, Edel meets a handsome young man with tall, black hair and an intelligent light in his eyes. Before long, their encounter develops into a situation that threatens the very survival of the kingdom...

(Source: Kadokawa, translated)