Ouji no Honmei wa Akuyaku Reijou - tập 1

The story follows an office lady who is reincarnated into her favorite otome game Hoshifuru Koi no Astrolabe as the villainness Diana. Prince Sirius gets close to Diana, although he is supposed to love the game's heroine. In an effort to prevent the bad ending which leads to the world's destruction, she seduces him. However, despite her efforts, the prince ends up falling for her.