In the nightlife area of Tokyo, Kabukicho, there are a lot of black Africans working as bouncers and touts outside of the club entrances.
Also some Pakistanis or Indians working in the restaurants and 711/Family Marts.
But I only saw them in that area which supposedly has a strong Yakuza presence.
Never walked into any of those clubs but I assume most of them are scams where you are forced to pay a padded bill.