there's a half-decent documentary about it on Netflix. I take it with a pinch of salt, as a lot of the doc was presented by Yakuza themselves, but the impression I got was that they're more like shady business consultants that probably have something dodgy going on behind the scenes

they're only allowed to continue to exist because of Japan's laws on cultural conservation

Interesting. The traditional take is: they answer needs that can’t be solved legally and enter business areas that have more risks than returns for normal people.

It’s familiar when looking at the prohibition period in the US for instance, where the mafia basically became an alcohol distribution network the day it was prohibited. Same in Japan: there’s laws on sex work, drugs, minor labor, gambling, money laundering, etc.

Yakuza groups will look at these laws and find the niches where regular businesses would be navigating minefields and blow up a thousand times, or where people will pay money for services only the yakuza can offer, and eventually abuse loopholes where they can take the money with low risk of anyone going after them.

Also the History of Japan podcast by Isaac Meyer has a good episode on the Yakuza, and several other episodes document how they have been involved with a lot of Japanese history.

interestingly, they seem to have a similar origin story to the mafia, in that they were originally law enforcers