Yes, Moon is a love interest that will be added in ep7. But in terms of main girls, only Gwen, Aine and Emma are the main ones. The rest are still LI's but not as major as these three.
You mean that the Sky isn't?! This forbidden love between "roommates" is pretty funny at first place. I should set is as cousins or something. Aine is obviously main, it's half a title drop. And Emma being the childhood promise would be the 'main who is set for L' if there isn't a harem ending option. But after these two, it feels like Sky should come even before Gwen.