From MangaHelpers:
One day, Son happened across a woman, named Shue, that he had loved as an older sister when they were young. It looked like it was the same woman, with the same scars, but Son had thought she was dead. In fact, she was a reanimated corpse, resurrected by a young girl named Fuu to work as her minion. Son becomes Fuu's follower, determined to find a way to return Shue's soul to her body so that she might live again. However, Son doesn't know what he's gotten into with Fuu, though, as she ends up in conflict with many other practitioners of her arts, using Shue's reanimated corpse to do things that Son would rather have never seen.