Mahou Shoujo Ikusei Keikaku: Red

Frederica, Old Blue, and Principal Halna clash over a powerful relic stored deep within the secret ruins underneath the old school building. A murderous intruder picks off magical-girl students one after another. Surrounded by enemies at every turn, Snow White stands before the entrance to the ruins that hold the fate of the world…and makes a critical decision. At last, Snow White’s long saga comes to a close! How will the story of this girl at the mercy of destiny conclude…? 

(Source: Yen Press)