In game they say over and over that a chapter 2 segment explains their past in high school. She only doesn't tell him just to likely get people to play thru that chapter.
Ive seen games where you don't break the girls and make them dependent on you. But they weren't really harem games. You can have a harem but it wasn't the focus. Like in Tales from the Void. Or in Once in a Lifetime. Lots of girls like you in both, but they never become shameless sex slaves that live to serve you the second no one is around.