Do I need to read Ruthless Boys and Darkmore Penitentiary?

Hello, I’ve been thinking about reading the Zodiac Academy and I know that the other 2 series are in the same univers. But I don’t like reverse harems. I don’t mind multiple love interests, but I don’t like when it doesn’t end with her paired with someone specific.

Do I need to read the other series? I’m a wrong about what reverse harem means for these books?