You mean the main theme/ story arc of this game?That's not what I mean. It's the plot point, the challenge the player/reader faces. Is it the creation of the harem the plot point? Or is it going to be something else? I know the game is named Harem Hotel, I'm curious.
Quite frankly, I don't think there is one. Dev might has\ had something in mind, but it is five years now. People change their mind all the time, and there is also reaction from players. So it is possible dev just dump whatever is in their mind.