If you're still in Osaka on the 4th there's
Hospital Gogo. Medical dress code is not compulsory but greatly appreciated.
The guy doing a live SM show at the event is the owner of a bar,
Kaliyuga, in Shinsaibashi. He's quite a prominent figure in the underground culture in Osaka, but it's a relatively normal bar, although there is a corner with a suspension point and ropes that you can freely use. He's also very knowledgeable about events and stuff. When i went there, while ordering my drink i said i love sweet stuff so he gave me a homemade creme brulee.
Otherwise you can go to
Witasexutopia, it's kind of an SM bar and the ladies are very cool.
As a woman they probably won't expect you to buy staff drinks, but if you come alone and monopolise one of the staff for conversation that would be a nice gesture to buy her one. They're not that expensive.
Club Doma is also an SM bar, but it's a bit more expensive, on some Saturdays they have a show late at night. I never went and i don't know anyone from there so i can't say more but if you google the name of the club you will find it easily, i think.
