I Married the Count My Sister Rejected - No Takebacks!NewI Married the Count My Sister Threw Away, So Don't Ask Me to Give Him Back Now; Imouto ga "iranai" to Suteta Hakushaku-sama to Kekkon Shita noni, Imasara Kaese to Iwarete mo Komarimasu; 妹が「いらない」と捨てた伯爵様と結婚したのに、今更返せと言われても困ります

Yuria is the elder daughter of the Braxton Marquis family, and she has one younger sister, Nia. Ever since Nia was born, Yuria had lived oppressed by her parents, who doted only on her younger sister. Nia grew up completely spoiled and twisted, constantly showing off to Yuria the men she went through one after another. Yuria had no interest in her sister’s boyfriends or bragging, but for some reason, the name of one young count had always stayed in her memory. Without ever meeting him, by the time she passed twenty, Yuria’s life began to change dramatically when she happened to attend a party as her sister’s stand-in—and met that young count, Jeremy Owen. https://www.cmoa.jp/title/354296/