Mahou Shoujo Shizuru

"Hey… you! Make a contract with me and become a magical girl!!"
Shizuru Murakami was met with this bizarre request from Emit, a fairy who claimed to have come from Etherland, a magical world different from Earth.
At first, Shizuru hesitated and refused.
But when she stumbled upon a scene where an unfamiliar girl was being violated by a rogue magic user—a "Violator"—she made up her mind.
She decided to become a magical girl, one who would hunt down these criminals.
What Shizuru didn’t know, however, was that her decision would lead her down a path filled with humiliation and suffering…

[Translated from dlsite]