That's a concession that must be made in a game like this, sadly, unless you go full manga or establish the girls as being into open relationships from the get-go (which could easily become so outlandish that it would require even more suspension of disbelief).
I've said this before in this thread, but if nothing else, I'd say Caribdis has markedly improved since OiaL, given how Orion is believably written as a good, pleasant person, womanizing tendencies aside. OiaL's MC, on the other hand, was often protrayed as a good person, only for the game to reward the player for