Atori Shou(2005)

Atori has an unusual part-time job... she’s a demon hunter! After school, she hunts demons for a mysterious organization named N.U.E. To kill her enemies, she unsheathes the saber hidden within her hair. However, Atori is actually half-demon, but she has forgotten her past. Despite this, she's been able to overcome many difficulties as well as befriend those from both species. Unfortunately, her once calm life is beginning to quake as a terrible shadow now looms over her...