Iwahada no Hanayome wa Ai de Tokasareru

Iwako and Sakiko Kamishiro are twin sisters born with divine powers. While her younger sister Sakiko is widely known as the most beautiful woman in the Imperial Capital, Iwako’s body is covered in rocky scales, giving her an ugly appearance, and she was shunned as a monster. She is mistreated even by her own family, and lives life little better than that of a servant. Iwako was drawn to Saionji, a jeweler who was the only one to treat her kindly, but it's her younger sister, Sakiko, who is chosen to be his bride. Instead, Iwako is ordered to marry Shiran Kuromine, an Imperial Army officer who isrumored to be "cursed by the gods.”

(Source: OnlyLips, translated)