ミスティリオン～少女の福音～

A certain village was once destroyed at the hands of a demon.

"The Tragedy of the Red Village - Crimson Flame".

...So the incident was called, with its sole survivor being a young girl named Aira.
Even though she's tormented by her past memories, she lived each day to her fullest.

One day, Aira gets lost on the way home after running some errands. In the silence of night, as she stood in fear with painful memories resurfacing, a young man appears before her on the verge of death; bearing severe injuries. Also, there was a black-winged demon silhouetted by the moon.