Apocalypse, then transforming into a magical girl

Post-Apocalyptic Survival Notes, Page 1: Abandon Morality and Fantasy. Magical Girl's Code, Rule 1: Believe in Bonds and Hope. A crimson storm, devouring reason, tears through the sky; terrifying monsters, savage and all-consuming, swarm the earth. Civilization crumbles in an instant; humanity loses its tomorrow. And you, little savior, your magical girl contract only signed until adulthood, yet you are already 17 years and 363 days old. If that single glimmer of light—is an opportunity for you, a wage slave, to also dabble in magic—then—let the torrent of elements burn away the twisted flesh, let the magnificent chapters of magic shatter the delirium of madness. Let solid barriers withstand the relentless onslaught, let boundless courage rebuild the spark of order. Let kindness be met with kindness, evil with evil, and let those who should not exist in this world be banished back to the endless abyss. This is the story of heroes, the legend of magical girls.