A few weeks ago, on a walk home from lunch, I passed this tiny "library" built into the fence of a private home.
Suffering from jet lag, I forgot to note where it was. Then I tried to find it, but couldn't. I made a map and crossed off the routes I'd checked. I began to suspect that I imagined it.
Finally today I located it on a walk to pick up blueberry mochi at Benkyodo: the Little Free Library on Sutter.