Yeah, the PC guide isn't clear. Though honestly if Kira corruption opens things up as was mentioned after you, you'd think her regular route would open these up as well, as that is still technically bringing in a girl.For Charlotte you need to bring a girl to the Red Maiden, that can be done by selecting rachel, monica or alice corruption route or bring Quinn to that old blind mafia man. As for June you would need to meet Charlotte and then visit the Red Maiden again to unlock June.
There are times I do wish the game didn't block off so much content on big choices, mainly because this isn't a VN where you can easily get back to the place you were before. My current save has around 370 days on it. I don't really have hours and hours to get back to where I was before.