Shoujo Tenshi Milcute
Miu's father left her five years ago with a box. The box was locked, and Miu's father took the key with him. on her birthday, he sent it back, and inside the box was a mahou shoujo transformation device! Now it's Miu's job to transform into Shoujo Tenshi Milcute and save the world!
This manga is about the forbidden love between Angel and Devil. (tenshi to akuma) There has been a war raging between Heaven and Hell for centuries--and it's Miu's job to find the "Heart of God" and stop the fighting.
EDIT: The author is putting this series on hold because she wanted to start Modotte! Mamotte Lollipop.