Haruka here is also a fake-y jerk who uses sex appeal to try and get men to do what she wants. The big differences are that she's filthy rich and doesn't care at all about actually finding love, (especially not with a guy.) She's also probably a few months younger than Charlotte, if Charlotte's 20? Haruka's about nineteen.

Some weird rivalry between the two of them would be amazing - Haruka's a Recolle native, but they can have met through college. She's all in on chemistry, which'd also contrast with Charlotte not really knowing what she wants to do. Alternatively, since they're on the same wavelength, they could have some weird hatefriends thing where they're comfortable showing each other their real faces?