The thing about incorporating player-created crime syndicates is that Vincent Albero's mafia is extremely powerful within Locke City, so we need to keep that in mind in regards to how his mafia would interact with another syndicate, and also not allow for a bunch of player-created syndicates because then that weakens Albero's grasp on the city -- which is currently not in the cards.
That said, I think there's some wiggle room. Japan Town may be a culture Albero mostly leaves to their own devices -- maybe he dabbles with them for the selling of drugs and illegal firearms, and certainly he's unlikely to turn someone from Japan Town away if they're a good candidate for loan sharking. There could be room for a yakuza group to emerge. The problem with that is Albero currently has the power to squash them.
Alternatively, there could be yakuza already, but if they wish to be successful, then they'll need to have made an alliance with Albero. That goes against what you previously mentioned about yakuza cold-shouldering non-Asians, but that could be a potential point of conflict if you're interested in pursuing it.
Re: GENERAL QUESTIONS
That said, I think there's some wiggle room. Japan Town may be a culture Albero mostly leaves to their own devices -- maybe he dabbles with them for the selling of drugs and illegal firearms, and certainly he's unlikely to turn someone from Japan Town away if they're a good candidate for loan sharking. There could be room for a yakuza group to emerge. The problem with that is Albero currently has the power to squash them.
Alternatively, there could be yakuza already, but if they wish to be successful, then they'll need to have made an alliance with Albero. That goes against what you previously mentioned about yakuza cold-shouldering non-Asians, but that could be a potential point of conflict if you're interested in pursuing it.