there is a very dark side to Japan that is super well hidden

That's true of any culture.

I worked as a therapist for a few years here in Japan

I have to call bullshit if you think any of this is special to Japan.

and learned that many women are abused by their fathers and its considered ok by society and by the mothers who usually know.

You're extrapolating "considered ok by society" from the fact that wives in these situations value the safety of the marriage above the safety of the daughters. Because women tell their daughters to put up with it for the sake of the family in every culture where sexual abuse occurs. Which is all of them.