When I go to Ueno or Akihabara (on foot or by bike), I often go through Yanaka Ginza and Ueno park. On the way, there’s a really short roofed passage. It’s the merchant street (a dead-end alley, actually) called Hatsune-kouji 初音小路.
There are several shops, restaurants and bars there with an atmosphere recalling a bit 1960’s Japan found in Yasujirô Ozu’s movies. If I have an opportunity, I’ll try one of these restaurants.