Bakko

The occult sword battle manga centers on a gloomy, introverted middle school girl named Bakko Shinno. One usual day at school, after Bakko finishes cleaning the classroom that her classmates have left her to do, she secretly goes to a shrine to pray for a peaceful life and the misfortune of extroverts. Suddenly, a demon(?) calls out to her and targets her, putting her life in danger.

(Source: Anime News Network)