From Operation Boredom :

Maiko Hananokouji, a descendant of an Onmyouji (a priestly occupation that involves demon warding), has the ability to chase away evil spirits known as the Jureiki. The Jureiki eats the souls of humans who commit crime after crime. As she continues to fight the Jureiki, she stumbles into a schoolmate, Ryou, who she saves from the Jureiki at one point. The two of them then begin to work together to ward off the Jureiki, but... !?