Perfect World: Devil Slayer

Ling Feng was an ordinary person born in Demon State. He went through numerous hardships and dangers and traveled across several states to enroll in Tianxian Academy. When he returned after completing his studies, his hometown was massacred and his only sister was killed. His black hair turned white overnight and he turned into a killing demon, just for revenge.
Later, with Qingyi's company, he transformed from a demon into a fairy, and the war was dark and turbulent.