I am willing to be a little lenient so for example if it is only 4 girls for part of the anime (Ex: K-ON) that is fine.
What is not fine is things that clearly have more than 4 girls (Ex: Azumanga Daioh) or if there is a guy (Ex: any harem) unless that guy happens to also be a girl (Ex: Kampfer)
Because I am a crazy person I need 44 different anime and here is my list so far
Spoiler :