This is quite a well established phenomenon, which highlights that a lot of gender gaps in developed countries really just comes down to choices that people make knowingly and freely.

> Paradoxically, the sex differences in the magnitude of relative academic strengths and pursuit of STEM degrees rose with increases in national gender equality

> A mediation analysis suggested that life-quality pressures in less gender-equal countries promote girls’ and women’s engagement with STEM subjects

https://journals.sagepub.com/doi/abs/10.1177/095679761774171...

Japan might not be a great example, but the Nordic countries are.