Sadly, 10x10 closed in 2014. A neighboring cafe owner told me that Takeyama-san closed the shop to take care of her grandchildren..I hope they appreciate her Max Roach records.
Hakuraku (白楽) 10x10 is a hidden gem of a cafe. It's in a residential part of Yokohama city (but only about 25 mins from Shibuya in Tokyo, on the Tokyu Toyoko Line) yet has regular live events at night. The lovely Takeyama-san has been the owner for the past 40 years. She's one of the world's top Max Roach collectors; there are portraits and photos of the great drummer/composer all around the cafe, all drawn by the wonderfully named "Asobi-nin no Kin-san" (遊び人のKINSAN)
I only visited 10x10 a few times but Takeyama-san always treated me like an honored guest. When I left last time she gave me a copy of Kin-san's book of essays and drawings about life and jazz as a present, proving yet again that jazz cafe & bar owners are generally among the kindest people you will ever meet. 10x10 is worth the trip out on the Tokyoko Line; after the cafe you can stroll along Hakuraku's famous old-town shopping street, and maybe grab a meal at the legendary TanTan Ramen shop.
Station: Hakuraku -Tokyu Toyoko Line (from Shibuya about 25mins)
Exit: West Exit
Distance from station: 1 minutes
West Exit, turn left down the little alleyway. At the end look left, you'll see the cafe on the 2nd floor.