Ryuu no Hime Brunhild

She was called the Dragon Princess by her people, sometimes with contempt, and sometimes with reverence. But 700 years before the Empire's cannon pierced the dragon's breast, there was another girl. Threatened by an evil dragon, the people of a small kingdom formed a pact with a Divine Dragon and flourished under its protection. Brunhild is born into the house of the Dragon Priestesses—the only ones in the land who can understand the dragon's words. Like her mother and her mother's mother before her, she serves the Divine Dragon, cleaning his temple, listening to his sacred words, and gratefully offering him tribute: seven people every month.(Source: Yen Press) Note: The setting is 700 years before the first published novel.