Jazz Haus Posy was opened in 1973 by jazz fanatic Misa. She's a serious enough fan to have traveled all around the world to various jazz festivals, as can be seen by the numerous signed albums and photos on the wall of the bar. (I'll have to ask her next time how the owner of a small jazz bar can afford to fly round the world 3 times a year to jazz festivals..)
The music is all vinyl, all classic jazz with nothing too heavy but nothing too quiet either. Like a lot of Japanese jazz bars, there's a portrait of Bill Evans in the bar though Misa will also play records with a bit more groove to them.
Posy is small and dark, the kind of place where it always feels like 1AM while you're drinking. There's a small buzzer on a table at the entrance; push that gently and Misa will appear from the back rooms where she seems to live. The seats by the counter are tiny and close together so be prepared to get intimate with the regular customers and electric heaters during the winter. Despite the closeness, Posy never feels claustrophobic. It's a jazz oasis in the crowded, noisy streets of Shimo-Kitazawa.
I recommend you visit there soon as I'm not sure Misa has anyone to take it over when she gets too old to run it (which from the looks of it, could unfortunaely be fairly soon..) See more pics of Posy over at Tokyo Jazz Joints.
Station: ShimoKitazawa - Odakyu/Keio Inogashira Lines
Distance from station: 6-9