Hagakure Sakura wa Nagekanai

This is a story of a boy saved by a god. It is also the story of the magical girl Hagakure Sakura, who was consumed by a demon. In a Japan threatened by demonic beasts, girls are forced to fight in a cruel war. They have made contracts with the gods, and people call them "magical girls" as they fight the beasts with their unique abilities. Nanase Tsugumi was an ordinary high school boy, except he had no memories of his childhood. One day, he was was seriously injured in a fight between the magical girls and the demon beasts. That was when the goddess Belle appeared and forced him into signing a contract to save his life. And so Tsugumi became the magical girl Sakura Hagakure. But only women are suppose to be magical girls. So even as Tsugumi fought as a magical girl, he was forced to hide his true identity. Meanwhile, demon beasts are stalking his only family, his sister Chidori… (Source: Earth Star Entertainment, translated)