@ansonh92 They are not little girls though. In Taisho era, the legal age for marriage was 15 years old. And little girls as young as 6 years old were sold to red light district to be Maiko apprentices so it is not unusual to see little girls there and police won't do a thing. They won't serve customers until they reach legal age and become a Geisha. Before that, they will serve other Geisha while learning etiquette, how to dance, play music instruments, etc.
After Ww2, prostitution becomes illegal and Geisha becomes strictly entertainers and don't sleep with their customers.