[@Rockin Strings]

I would imagine that it might be some sort of narrative that introduces the area. Maybe all of them are in the same school - a school that has a middle school up to college or something.

Maybe you could add on why the Guardian chose them in particular, if they already have their Miraculouses by then for maybe a week, and then imply of the danger that is looming over them.

Bringing them together as heroes would probably come from the villain's attack. But if you want them to partially meet as normals, then probably having them in the same school would be ideal. It's just an age difference, doesn't really mean that they can't meet.