Maou-gun Shitennou no Saijaku Reijou wa Jiyuu ni Ikitai!

Oh, crud, I just realized that I’ve been reincarnated into my favorite manga as the first boss defeated by the heroine at the start of the story! Worst yet, it turns out my fiancé is the strongest of the Four Grand Magi and the very villain who slanders my character as a disgrace on her deathbed! I’m outta here! This is the story of the weakest manga villainess who seeks out the slow life instead of the villain life. (Source: Cross Infinite World)