I'm gonna pipe in: Does every little thing really need to be spelled out immediately? ^^"
We've seen plenty of the past (rejection, maybe due to family circumstances or something because Setsuna is so all over the place about it, with Yuga experiencing it as someone who's watched over them as a friend), we've seen the black-haired twin get pissed off by the letter and tear it apart, I'd say it was her before, too (sis-con?). These are pretty typical developments for the genre.
This is not so bad as to deserve nothing but complaints in the comments. Let's calm down, shall we?