Puella Magi Kazumi Magica, Vol. 4: The Innocent Malice — Masaki Hiramatsu

From the very start, it was Kazumi who drew the girls of the Pleiades Saints together. But no magical girl, however beloved by her friends, is exempt from the fate that awaits them all. Fearing that the evil nut may be accelerating Kazumi's transformation, the girls are divided - can the process be delayed, or should they take out Kazumi while they still can?