@Massaovs Elementary school in Japan runs through 6th grade, so the kids are going to be mostly between eleven and twelve years old. But also many kids,
especially girls do it innocently like she's describing here well before then. For more on that, let me ping in two others...
@henman @smolbaka Little girls do discover rubbing themselves down there feels good at an early age. It's not remotely unusual to see toddler girls rubbing themselves in public, usually to their parents' dismay. But you can't really call it masturbation at that age, because they don't... I guess follow through is the best way to put it. They'll rub themselves for a little bit because it feels good then stop.
It's after puberty starts that it gradually becomes masturbation, with rubbing sessions lasting longer causing the eventual discovery of orgasms. People also tend to underestimate when puberty starts in kids: it's usually between ages eight and thirteen in girls, and nine and fourteen for boys. In the US elementary school ends with 5th grade, so kids will be close to eleven before it's over. In Japan it's 6th, so close to twelve. Masturbation before the end of elementary school is
very normal.