When talking about "The Home Harem Event", I guess you refer to Bree and Sasha? You need to have sex with each girl within 7 days (top of the page https://wiki.andrealphusgames.com/wiki/Home_Harem )
Regarding Minami, besides double checking the prerequisites (https://wiki.andrealphusgames.com/wiki/Minami#Practice_dating), I can't help without a little more context.