Well, in a pure Harem game, everybody ends up in bed together, which, while pleasant, is not how things usually work out in real life, and consequently those games are usually unrealistic.
While, in a Polyamory-relationship game, the girls don't all live with the MC, but they accept that the MC has other lovers. It's a way for the player to have the MC hit on all the girls in one playthrough, and not get killed by one of the jealous LIs.
However, it is unlikely that either of those options will be available in THIS game. You will probably have to have your MC make choices on which one to end up with.