Return of the Demonic Instructor

Story

The world is destroyed by a demon invasion and Bigang Sa is forced to serve in the demon army for centuries. After a failed human uprising, Bigang transports himself back into his body, ten years before the arrival of the demons. Can he use his centuries of demon warrior training to create a new class of murim fighters powerful enough to ward off the coming invasion?

Inhaltsangabe via AniList (Englisch).