I think the game is going to be more sharing than harem: Almost all the "LIs" (to call them in some way, although in reality none of them include Love in their possible relationship with the MC) freely sleep with all the guys in the island. The only LIs (with real Love) exclusive to the MC are his sister and his mother (or whatever you want to name them in the game) But, I think the Dev doesn't really intend to show many scenes of other guys fucking girls either.
For the rest, I think that the developer already said sometimes that he doesn't like the NTR, so there is not much chance that it will include in the game (rather none)