You basically need to find another couple that both speak japanese and combine to make 2 couples that one person in each group can speak japanese.
The reason is that olive21, the couple kissa in Tokyo, requires 1 person can speak japanese in a pair.
You might want to try to find a couple on these boards that will go with you to a normal happening bar and try to do swapping there too. Club Scarlett is well known for for couples, but it does require japanese so you will need someone to bring you and be a translator.
Voluptuous is the most common bar for foreigners but there are always many couple available for swapping. It's not impossible, just less likely.