Oh yeah, one point I forgot to add in [url=https://youtu.be/k8mqs1rGRY8?list=PLNzvP_1n68VsBnGZjLRZV6ADnpMPWSzi_]the other post[/url], OP: in the 70's there were more (smaller) street gangs in Japan, and violent clashes between them were very frequent. In the 80's, most of these gangs had formed larger [i]rengō[/i] (alliances); battles between these [i]rengō[/i] were rarer, but when they happened they involved far more participants, often numbering in the hundreds. And finally, the decline of Japanese street gangs began in the 90's and continues well into the 2020's. There are still gangs kicking around Japan, but very few of them, and even then some of them just like the fashion and have turned the [i]tokkō-fuku[/i], the [i]tobi[/i] pants, and misc. delinquent fashions into innocuous streetwear, representing no allegiances or deliquency. Four digits at most of gang membership these days, whereas the [i]bōsōzoku[/i] (e.g.) hit an all-time membership around 43,000 (forty three THOUSAND) members nationwide in 1983.

So in addition to the reasons already given, the decade you choose also determines both the culture and the relative danger of the gangster lifestyle in Japan. Both from cops and from other groups.

I recommend watching [i]Godspeed You! Black Emperor[/i] for a taste of what it looked like in the 70's. [i]Sayonara Speed Tribes[/i] for the 80's.