Don't worry there, I play both Netori and Sharing route, and so far on my Netori route, i didn't have to share any girl with another, okay some still dating another guy, but they didn't do anything with them, same on the party on not share path, none of the girls will bj their partner. Only on the share path they will even if you didn't improve relation with them yet. I made Ella my first girlfriend, and several are crushes and the green haired is also my gf since this last update. Although I don't see the harem tag, it seems you can eventualy be with all of them as their first at this look.