Kore wa Zombie desu ka?

Aikawa Ayumu is a normal high-school boy, until one day he is killed by a serial killer. The necromancer Eucliwood Hellscythe revives him--but as a zombie.

As he begins serving Eu as her guard, he happens to deprive a mahou shoujo (magical girl) named Haruna of her magic power. Haruna orders Ayumu to take her place and fight against anti-mahou shoujo system, "Megalo."

From Yen Press:

Life—or undeath?—isn’t easy for Ayumu Aikawa. A seemingly normal high schooler, he is in fact a zombie who serves as a bodyguard to an introverted necromancer. But his already complicated existence becomes even more outlandish when he accidentally steals the powers of a magical girl, transforming into one himself—complete with frilly dress and pink chainsaw!! How’s a reanimated corpse supposed to keep his head on his shoulders with roommates like these girls around the house?