Magical Girl Apocalypse Vol 1

Magical Girl Apocalypse by Kentaro Sato. A Horror manga rated Older Teen, published in English by Seven Seas.

An ordinary school day turns into a nightmare when a horde of grinning, murderous magical girls appears out of nowhere and begins slaughtering everyone in sight. Anyone they kill rises again as a zombie, and Kii Kogami must fight to survive as the outbreak spreads across Tokyo.