She's the Duke

가짜 집착광공에게 집착하는 진짜들, A Verdadeira Obcecada Não Sou Eu, Gajja Jipchakgwanggongege Jipchakaneun Jinjjadeul, She's the Duke, The Maniacs Are Obsessed with the Fake, The Real Obsessed Ones Who Obsess Over the Fake Obsessive Maniac, Top Toxique malgré moi, ヤンデレ

As if reincarnating into a whole new world wasn't enough, Lewin was reborn to a father so bent on having a male heir that he used dark magic to disguise her as a boy. Over 20 years later, she finds an unexpected ally in a freshly-transmigrated fellow Korean girl. However, this new friend delivers shocking news: they're in a tragic BL novel in which a love triangle will ultimately lead to the apocalypse! Still, if Lewin can seduce the male lead first, they may just manage to save the world...

(Source: Tapas)