Sleeping Beauty is probably the best Happening Bar in Shibuya. It’s a bit private, entrance looks like a convenience store. There’s a door bell outside, you need to ring it and they will let you in. You might need someone who speaks Japanese to come with you, most people there are Japanese and don’t speak much English.
The club is fairly large (4 levels), so it’s one of the biggest swingers clubs in Shibuya. Most of the swinging happens on the first or second level (floor) and the other floors are for socialising.