Imouto ni Konyakusha wo Yuzure to Iwaremashita: Saikyou no Ryuu ni Kiniirarete Masaka no Oukoku Nottori?

Lady Eliana of the Ducal House of Lumiere has finally won the hand of Crown Prince Alvin. All her life, Eliana trained to be a suitable bride, pushing herself to be the best she can for the sake of her family. However, their dream that she has worked so hard for is shattered on a whim by her little sister Luna. Having fallen in love with the prince at first sight, Luna demands that she become Alvin’s fiancée. Her doting parents are more than willing to oblige, so the two sisters are switched, tarnishing Eliana's name in the process. In her despair, Eliana volunteers to be the "Dragon's Bride," the maiden ritualistically offered every 10 years. Although she hopes to escape through death, she is surprisingly saved by the dragon Greed! Taking a liking to the estranged Eliana, the mythic dragon proposes their marriage; grateful to escape the clutches and shame of death, she accepts. What adventures await the outcast noble in such a peculiar union?