That's because the sister didn't quite let go of the past, but has now moved on and let the past go to embrace her new path forward. Needed to have the characters grow, so of course they'll make it focus on a character that was in the midsts of a breakthrough.
I just wished they didnt made this into a “p0rno” story because this is so well done and describe such a very scary side of the world. Like this story got my heart palpitating and actually in my feels, its just so well done story wise. The nasty disgusting r4p3/sa scenes ruins :/
Oh wow this is such a good premise to a very repetitive form of manga. Ive been enjoying it a lot