For homicide/fertility/etc rates, a simple google search will give you numbers.

For sexual assault/corruption/etc, it’s honestly common knowledge at this point. Googling “Japan underreported crime” will give you plenty of results from a variety of sources.

Additional insight comes from having a few close Japanese female friends who have opened up to me over the years.

If you’re trying to cure yourself of the “Japan is a magical place” myth, I highly recommend “Making Common Sense of Japan”, written by an economist. It’s from 1989, so the data is dated, but most of it still holds to day, and the analytical frameworks it builds are just as relevant.

There was a blog post written on the subject that I saw on HN a long time ago that I will try to dig up, and will update if I find it.