It's actually more of a social issue rather than a legislative issue.

The vast majority of hunters live out in aging, rural areas. Areas where young people are moving from to more urban cores like Tokyo, Nagoya, or Osaka.

Additionally, hunting isn't seen as a "leisure" activity here; it's seen as a job. One that doesn't pay that well either.

Getting a gun license here isn't hard, takes a couple of months, mostly of just waiting, at worst. The police will do mental health screenings, financial reports, social screenings, and a few other risk vectors, which take a bit.

Source: Actively going through the process.