There's plenty of ways to approach Japanese-American crime roleplay. You could obviously go for the Yakuza schtick, which is impossible with the current stigma around it, and it's frankly overdone and romanticized to death. I'd say your best bet is to look deeper into it, find realistic circumstances that Japanese-American youth would band up. You can do some digging through some (credible or uncredible) sources and find instances of Japanese-American street gangs existing in L.A. (i.e. Marshall Homeboys, Buddha Crips, Tokyo Boys, & Westside Japs).
Your best bet is to take liberties as to how a gang originated in these parts. Most waves of immigrants come from historical events, for example a wave of impoverished Korean immigrants came to the United States during the 60's due to the Korean War, and to fend off against racial stigma and the issues of poverty, they formed gangs.
So, your goal of having a 'Yakuza' isn't likely, you're not going to be chopping fingers off or having full irezumi tattoos anytime soon. However, if playing a Japanese character is a must, you can use these sources and whatever else you have to piece together customs of defunct and disbanded gangs, and form your own circumstance about it. The argument of creative freedom is thrown about willy-nilly for the creation of Yakuza roleplay, you can't apply Yakuza gangs taking prominence in the U.S., currently. What you can do with this creative freedom, however, is create a circumstance where a gang of Japanese youth is created, and then make yourself prominent through IC circumstances, such as LCN did.
Now, you might have the argument; "LCN only took prominence in character through every Tom, Dick and Harry wanting to play an Italian mobster like its the sixties, seventies and eighties." Now, think of the fact that you can apply that to a Japanese gang, as well. There's already a substantial amount of people roleplaying Japanese people, in combination with a fledgling gang, there's no reason you couldn't establish yourselves by sheer manpower.
Seriously, try it.