Some of these places may accept you if can communicate well in Japanese, but a great number don't care about your skills, just your face. That said, there are some places around that see the potential and are beginning to care only about the color of your yen and not your skin.
When it comes to While brothels are still technically illegal, the ones there still survive because of a grandfather clause loophole in said law. To get there, you have to walk about a mile north of the Asakusa area to an area that's about 2 blocks long.
Word to the wise, though - foreigner-friendly places expect foreigners to not understand Japanese, so there will be some light scamming.
Also, the pictures used to select the person you want to see is generally airbrushed, but the more high-quality read: expensive the place, the less likely this will happen.
The Yakuza runs by a different set of rules than many gangs in other countries. They generally don't mess with foreigners unless the foreigner does something particularly nasty to them. There is a standard printed placard saying no dogs and no foreigners.
