Aisareseijo wa Yami Ochi Akuyaku wo Sukuitai

Sphere, the daughter of an earl, has been confined to her mansion since she was a child due to her lack of magical powers. When her stepmother and stepsister arrive after her father remarries, she realizes she has been reincarnated as the heroine of an otome game. She immediately uses her knowledge of games to acquire the powers of a saint and enrolls in the magic school where the game is set. Her goal is to marry Ewald, one of the characters she loved even before her reincarnation. Then, she must save the villainous character who has fallen into darkness and find happiness