Otome Game Heroine no "Hikitateyaku no Imouto" ni Tenseishita node Tachiba wo Ubatte Yaru Koto ni Shita

Stella is the kind of airheaded, tactless older sister who’s somehow loved by everyone. Mimosa, on the other hand, is the socially awkward, naturally isolated younger sister—and an easy target for bullying. Mimosa reincarnates into the world of an otome game she played in her previous life, as none other than the twin sister of the heroine, Stella—a mere supporting character meant to make her sister shine. If the story follows the original scenario, Stella, who aims to become a Holy Knight, will eventually be the one to bring about Mimosa’s downfall. …Yeah, no thanks! Determined to avoid her grim fate, Mimosa teams up with Chiro, a slightly dangerous guardian spirit who has fallen to the dark side, and decides to flip the script and rise to the top. After meeting the Holy Knight Sir Leonhardt in the forest, Mimosa becomes his disciple. As she throws herself into relentless training—yes, including lots of muscle workouts—the wheels of fate begin to turn, and the “scenario” itself starts to change… A reversal fantasy about an unfortunate girl who refuses to accept her doomed role! https://www.cmoa.jp/title/348795/