Let me see if I can help. The setting is original, but the universe is based on Slavemaker 3? If so, then this would properly go in Games >Misc, and you would need to tag it as AU, and disclaim ownership of Slavemaker 3 as well as all anime or manga from which you've taken characters.
As an example, it might read as follows:
"I don't own Slavemaker 3, Bleach, Death Note or Inuyasha. I make no profit from this work."
Obviously, I'm using random anime to illustrate, but that format works for us as a disclaimer.