MUNOU SAIJO WA AKUJO NI NARITAI: GIMAI NO MIGAWARI DE TOTSUIDA REIJOU, KOUSHAKU-SAMA NO DEKIAI NI KIZUKANAI
Other names: 無能才女は悪女になりたい ~義妹の身代わりで嫁いだ令嬢、公爵様の溺愛に気づかない~, An Incompetent Woman Wants to Be a Villainess ~The Daughter Who Married as a Substitute for Her Stepsister Didn't Notice the Duke's Doting~