Though bars like this have been steadily declining in number since the end of Japan's bubble era, you may still run across a few while walking through the city (especially Ginza). As the name indicates, members-only bars require you to be a member yourself or be the guest of a member. Usually you'll be required to pay some kind of registration fee in addition to yearly membership dues for the privilege of drinking at that particular bar.
Whiskey Richard is the founder of nomunication.jp, and has been saying he has lived in Japan for ten years for the past four years. He enjoys drinking basically anything except straight-up Campari.