Japan will lock people up for a long period of time if they show the sort of anti-social behavior that the most visible homeless people in North America are famous for.
It is not because the US doesn’t lock people up enough.
Try to be charitable in your interpretation.
Once again, I don't know much about Japan but I doubt there is a large ethnic minority that is only about fifteen percent of the population but somehow accounts for almost half of all incarcerated people in Japan.
From Google:
> Low Incarceration Rates: Japan maintains one of the lowest incarceration rates in the developed world (roughly 35 to 40 prisoners per 100,000 residents, compared to over 500 per 100,000 in the US).