Gensou Nanatensei Den ~Maki no Ichi~

20XX, April, a lone schoolgirl rides the night train to her new school, St. Academy of Heavens.

Suddenly her world is plunged into red, and creatures from the depths of darkness swarm on the schoolgirl. She uses her demon hunting special ability. She is such a person.
As a demon hunter and one of the Seven Saints, her role in the great war has begun.

The first of three chronicles.

from DLsite english: https://www.dlsite.com/eng/work/=/product_id/RE101964.html