Viscount's daughter Claris, who lives in the royal capital, has always been compared to her beautiful sister, also known as her "jewel of Fahrenheit," and has been oppressed by her family and lived in the shadows inconspicuously. She will be married at the age of nineteen, in place of her sister as a reward for the results of the battle of Siegfried Gutenberg, who is known as the "Cannibal Margrave." However, Margrave Jean is a charming person who has a silent and expressionless personality but is caring towards Claris. However, Claris, who feels guilty of being a "substitute bride," could not easily entrust her heart to Jean. When the news of her sister's marriage arrives from the royal capital, she and Jean are heading back to the royal capital... In fact, Claris's birthplace has a serious secret?! What's more, the marriage with Jean is different from what Claris knows?! 王都に住む子爵令嬢・クラリスは、「ファーレンハイトの宝石」とも称される美しい姉と常に比較され、家族に虐げられ、目立たないよう陰で生きてきた。クラリスが十九の歳、「人食い辺境伯」と呼ばれるジークフリート・グーテンベルグの戦果の褒賞として姉の身代わりで嫁ぐことになる。ところが辺境伯ジーンは、無口で無表情ながらもクラリスを思いやる、包容力に溢れた魅力的な人物だった。しかし「身代わり花嫁」であることに負い目を感じるクラリスは、なかなかジーンへ心を預けられないでいた。そんな折、王都より姉の結婚の知らせが届き、ジーンと王都に向かうことになり……？　不遇の令嬢が辺境の地で最愛の人と幸せになる王道ラブファンタジー！