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.