Maybe you're not getting what I mean by a GANG. Bosozoku is a BIKER GANG... you know, like Hells Angels?? These are the low-life people in Japan that will send you what's left of your wife and kids in a ricebox, after they put their bodies through a wood chipper. They operate through drugs, theft, vandalism, and being outright offensive, hence the ridiculous cars, obnoxious revving, and mob mentality. If Japan's police can't stop them, I'm positive you're not, with or without a weapon.
They might look wimpy, retarded and pathetic, but I assure you... they give zero fucks about anyone else. Like I said, I'm shocked someone even took the risk of even documenting what they do and who they are, regardless of how vague they were being about what they actually do. This isn't the stuff you see played out in the movies.. it's real life.
True... Bosozoku style is the idea that you're loud, offensive and ridiculous. That's why you see such crazy stuff when you google bosozoku cars. The one you posted isn't really Boso at all, but closer to what they call, "Yankee" style. But it all stems back from Bosozoku bikes, which at one point were simply out of control and terrorizing Japan. As an American in japan, if they saw you driving around a Bosozoku style car or bike, you'd likely get your ass kicked or killed... the true gangs would be very offended. It's not something you can just do.
Didn't you live in Japan for a good period of time? I'm sure you're speaking from experience.