Mahou Shoujo Tokushusen Asuka

A violent interdimensional race known as the Disas first came three years ago, destroying everything in their path on Earth. Humanity's sole chance of surviving depended on those who transformed into magical girls after forging an alliance with the Spirit Realm, who had followed the Disas to Earth and rendered normal weaponry ineffective. The group of magical girls triumph after a bloody battle, and the survivors are now referred to as the "Magical Five." The Magical Five split up after the conflict with the Disas. Asuka Ootorii retires and enrolls in high school, but Kurumi Mugen, Mia Cyrus, Tamara Volkova, and Lau Peipei individually continue their own military career. Asuka's tranquility, however, is fleeting because it appears that there were survivors on the other side of the conflict. Asuka is forced back into fight as an even worse conflict approaches since magic must be combated with magic.