Ryuujin no Saiaikon: Suterareta Hime Miko no Koufuku na Yomeiri

"A beauty... So otherworldly it's frightening." For generations, the Kuguu family's daughters have been born with purifying power, acting as shrine maidens for the village. Yuzuki was born into this family as the older sister of twin girls. While possessing purifying powers far greater than that of her sister, Mizuki, she is neglected by her family due to a mark that resembles a dragon on her back, which is seen as an ill fortune. The family conveniently uses Yuzuki's powers to make Mizuki look like a princess shrine maiden, who the villagers deeply admire. Tired of being used as a tool, Yuzuki dreams of her freedom and leaving the family to find the source of the mysterious voice she's heard occasionally since childhood. However, when that dream is crushed and she falls into deep despair, a God of calamity in the form of a huge dragon appears in the sky. Yuzuki is offered as a sacrifice, and she suddenly sees a flashback of her past life. Then, a dragon god, Sogyoku Seotsu, appears in human form and embraces Yuzuki. "I'll never let go of you again... My bride." The true princess shrine maiden is offered as a sacrifice in her younger sister's place and learns of the promise made between the dragon god and his bride in her past life. (Source: MangaPlaza)