The Woebegone Wonder Girl Wants to Be Wicked
Munou Saijo wa Akujo ni Naritai: Gimai no Migawari de Totsuida Reijou, Koushaku-sama no Dekiai ni Kizukanai
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～
Munou Saijo wa Akujo ni Naritai: Gimai no Migawari de Totsuida Reijou, Koushaku-sama no Dekiai ni Kizukanai
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～
Source
From Bumbling Prodigy to Villainess: Will the Duke's Love Go Unnoticed?
Munou Saijo wa Akujo ni Naritai: Gimai no Migawari de Totsuida Reijou, Koushaku-sama no Dekiai ni Kizukanai· 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～
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Despite Avril's unique ability, her family has always treated her like a bumbling waste of space. Eventually, her parents force her into a marriage of convenience in her wicked half-sister's stead. Contrary to the rumors, however, the decrepit, lecherous Duke Lanchester turns out to be a gorgeous young man. Of all things, Duke Lanchester wants to marry a villainess for three years before divorcing her. For Avril, this is the perfect opportunity to secure her freedom in the future. Thus, the oddball prodigy must do her best to play the villainess, simultaneously bewildering and charming everyone around her! (Source: Cross Infinite World)