Yeah, the Yakuza is a relatively tame organization compared to western mafias or even the neighbouring Chinese triad gangs. And that's why they're able to live so out in the open, with offices and everything. As a matter of fact, most of their money comes from real estate scams and extorting large companies, as opposed to more traditional criminality, such as drug trading. The one thing they are notorious for, however, is human trafficking, but I guess that might be a bit of a grim theme to open the game with.