Why i still have a bad feeling about rix's sister and that fruity couple?

I feel like she's just being over protective big sister since she haven't seen him for years and i think that her mind set it's like that the mc still is innocent for some reason that he's still a kid and she doesn't wanna accept the fact that he's a grown ass adult

yea makes sense,but I'm nervous since the author said big things are going to #－.－)

happen*

I'm just waiting for the seme to finally show he's dark side tbh like can he just snap