Well, based on Caribdis's previous game, It's highly likely that the ending of this game will have a harem route included, that is if you managed to remain in a relationship with the girls that you want to be part of your harem. And don't worry about options leading to a dead end, if Caribdis will imply the same system that they did with Once in a Lifetime, there will be plenty of choices that will be presented to you all throughout the game to help you steer clear of said dead end in order to achieve your desired ending (harem or just one specific girl). With that being said, I think it is safe to say that there's no need to hold yourself back from being attached to the characters that you like. But if you're still having second thoughts, I really recommend you to try Once in a Lifetime first since it will be much better if you experience it first-hand, also I cannot emphasize how amazing that game was. I hope my answer helped you somehow.
P.S.:
I am not in contact with Caribdis nor do I have any insight on how they intend to develop this game, so there is still a possibility that they might not implement the same system that they used with Once in a Lifetime. We'll just have to wait and respect on how Caribdis will proceed with the relationship system in game.