So I'm guessing since the Rita's father is a merchant, he'll eventually meet some trouble with his business where the only way out would be to marry his daughter to a different family that can support them. That's one way I can see drama unfold. Otherwise, maybe someone in Rita's family gets a sickness that only a noble family can get an advanced doctor to cure, but they'll take Rita as a wife for the price? Either way, Rita and Kan will get back together somehow. Personally, I'd like the second scenario as it gives Kan a chance to prove himself by finding a treatment as well as developing his reputation; possibly causing more nobles (or their children) to seek him out. Really enjoying the slice of life and sugar-coated chemistry nonetheless.