Concept: An idol group that has clearly defined roles, where not every girl is "the nice and cute one", but follow a more boyband formula with the bad girl, the pretty one, the young one etc.
//Edit: I'll just add them all with time
//Edit 2: Boyband Formula Idols complete
The bad girl
Forced to join the school idol club after multiple incidents so some more behaved girls can keep an eye on her, and so she'll be too busy to mess up anymore. Hates it at first but warms up to it a little, though she still reacts to a lot of things with an "Ugh" attitude (mostly charity concerts and other festivals to widen popularity) and is the roughest with her fans (which they love because Wow she's so wild, who can tame her!)
The strong silent one
An exchange student who was at a sports club at her least school, but can't really do it anymore due to an arm injury. Was one day strolling around the school grounds when still relatively new and saw somebody struggling with carrying some boxes and helped them out. Turns out they were part of the idol club and so she helped them out a few more times and ended up joining. Nobody knows why she switched schools, how the injury happened or even what club she was in since she doesn't really talk much. But she gives great hugs and her fans swoon over each one-syllable-answer she gives.
The young innocent one
Made to join the idol club by her older siblings, with the hopes that working with others and performing in front of people would help her gain some life experience. Prone to getting lost, struggles with heavy objects (thank god for Strong Silent helping her out with that), but loves coming up with fun ideas for shows and for member bonding. Probably has the most knowledge about idols.
The class clown
Always the one who has a joke ready in class, she's full of fun ideas and was asked by the idol club a few times to help out with conceptualizing new shows and found the insight she got so much fun that she ended up joining. Ends up lightening the mood always, even if she can be a bit TOO much sometimes. Welcomed the Bad Girl first. Choreographist.
The pretty one
Founder of the idol club because man does she love attention. Most likely to skip school on a bad hair day. While aloof, she's still really nice especially once you get to know her, and makes sure to keep the idol club running smoothly, though she appreciates the help of Strong Silent in the background. Sometimes exchanges Make-Up tips with Bad Girl once they warm up to each other. Often swarmed with fans who ask for pictures with her.