On the UES in the 50's, there are these discreetly located doors up along the avenues with Japanese lettering. Curious (and hoping to find something), I stumbled into a few around 3 years ago looking for some UTR Japanese spas. Instead, I found multiple hidden but fairly obvious (if you're looking for them) Japanese bars scattered in the upper 40's to 50's. All of them immediately spoke to me in Japanese - which I do NOT understand. And in one place, there were 2 hot girls sitting at a bar just looking awesome. I was denied entrance in all of them.
I seriously considered learning how to speak basic Japanese for a short while just so I could get in and see what these bars were all about. Sadly, I'm too lazy and can only say "Domo Arigato Mr Roboto."