Wow, is this the first time they've had one of these "dismissed from the hero's party" stories where there's no backstabbing, NTR (well, then again, not sure what the MC's exact relationship is with glasses girl), edge, revenge etc?
Interesting hint with that pawn to queen analogy. We know this game will be pretty cut throat, though it's still unclear why the prince is doing this.
As far as Apple goes, I guess she's a candidate of sorts and doesn't even realize it.
Catherine, like her namesake Catherine of Aragon, is from S Kingdom (Spain)
This is E kingdom (England) at constant war with the "Northern barbarians" (Scotland)
Sumire is from the small B kingdom (Belgium)