Nozomarenu Hanayome wa Ichizu ni Koutaishi wo Aisu

She's an "unwanted bride," but she will do anything for her first and only love, Keith, to smile and be happy...

Tinaria, an unfortunate bride who was sent to an enemy country as a hostage after the defeat of her country, Lidea. The people are momentarily fascinated by the beautiful bride who becomes the wife of the crown prince, but then they remember Lidea's atrocious behavior and turn to hatred. Tinaria, on the other hand, has been single-mindedly devoted to the crown prince, holding on to precious memories from her childhood. Although she was born a princess, she was shunned by her family and treated as little more than a servant, but he was the first person to smile at her...

But when her husband, Keesfalt, coldly tells her that he has a lover... everything starts to go downhill.

(Source: Bunkasha, translated)