I've been making a walkthrough as I go, and this is how it looks right now:
You use the talk choices to gain affection with the girl of your choosing. Once you get enough, you unlock a scene with her. Rinse and repeat until you finally lock yourself into her route.
In the meanwhile, there's also a 'common route' thingie where it just plays random daily life scenes as long as you don't lock yourself into a route. These don't reflect any of those choices or girl-specific scenes, since they're more of a generic common route. But that's fine. They're just filler.