@someonenoone11 alright.
Yuri's a loner and she thinks the're alike. So, she's trying to get closer since she thinks she's found someone who understand her.
Nemo coz she got teased really hard back then. She was petty and wanted a pay back. Then she grow a bit and now she want to be able to talk without filter or shame like Kuroki.
Asuka coz she's a mum friend, Kuroki got her soft side and currently she's pushing hard for Kuro to treat her as a normal friend instead of some kind of idol... and she's beginning to getting desperade.
Ucchi is a creep. She thought Kuroki was obsessed with her because several misunderstanding no one dared to clarify. So, she's now full obsessed with Kuro and want to know and be as close as possible to her to be sure Kuroki isn't trying to do the same thing she's doing... yeah. At this point her friends may think she's a lesbian.
All the other girls are basically like "what the hell with this quiet and gloomy girl and why so many different personalities are close with her?"... and then they try to interact with her and only get progressively more confused, so they want to interact more with her to understand what's going on...
To reach this point several in-universe months, years has passed to end up like this.