There will be Harem, it is part of the story itself. There is also the possibility of other tags.
Okay so will the main character have the only sex scenes in the game?
not quite. ie there will be scenes with the orcs capturing female slaves or with the Bitch King harem (just as an example).
Those are optional. A simple example: if you stumble upon a pack of orcs that captured a girl, you can fight them off, you can spy on what they are doing (and hence watch them having sex) or you can leave.