Synopsis: Imouto to Kekkon Aite o Koukansuru Koto ni shita ~Reitetsu Henkyou haku o Zenryoku de oshimasu!~

The calm and composed noble lady, Séverine. At a ball her business-minded father attended to find a fiancé for her younger sister, Séverine experiences a fateful encounter. — The Marquess of the Frontier, Nazaire. Supple muscles, a sharp and handsome face, and a ruggedly masculine build. He's her super miracle ultimate type!!! However... he’s actually a candidate to marry her sister. Disheartened, Séverine resigns herself—until her sister unexpectedly refuses the match. It turns out the sister has feelings for Séverine’s own nominal fiancé. “…Then why don’t we just swap fiancés!?” Now aiming to reach the altar with her dream man ☆ The (supposedly) cool noble lady's grand proposal strategy begins!!