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

Eliana has done her best to be chosen as a fiancee of the prince, and the day her wish come true is here. But she never expected that her younger sister falls in love with the prince at the first sight, and begged to be the fiancee instead of Eliana--and her father and the king approved it. She decides to jump into the magma to be the "Dragon Bride" and sacrifice herself for her family(father approves again!).. And something unexpected happens again---the legendary dragon Greed saved her from death and took her to his den. Greed decides to marry her according to the legend. And Eliana's life as the Dragon's Bride has begun!

(Source: Kadokawa)