Actually, the game is a full game. However, it is fairly short. Well, each route individually is anyways. If you combine all 3 in total, it isn't nearly so short.
A sequel is an interesting idea. Tbh I've never considered it before. But now...
I know, but You can expand the Universe...maybe, what happens when You date them, their backstories, a plot twist, a central villain or rival who wants the same than You...
Further dates, cementing the relationships could be an option. Further artwork, explicit and or otherwise would be welcome. The style is not one I've seen often in this genre and like the creator I'd like to see more of it. In any event, thank you for this. It's great.