The Elf Princess in the Maid's Dress

Elvira, an elf princess, flees an arranged dragon marriage and binds a life-death contract with Prince Cain. Disguised as a maid, she uncovers her parents' sealed past. Together they defeat Duke Gregory's conspiracy to revive the Demon King. Elvira learns she is the Demon King's seal. They sacrifice their souls to win, are crowned king and queen, and purify the demonic energy. But at their daughter's birth—has the remnant poison truly vanished?