Along with Ueno Park, the used bookstore district in Jinbocho is one of my favorite places in Tokyo. I spent hours browsing there earlier this month. I have found so many invaluable books there over the years.
Recently at Jinbocho, I found this gem. Published in 1939, it includes the most important primary sources to focus on the origins of Mitogaku.
The Imperial Chrysanthemum on the front cover is interesting (1939).
[The photo of the Jinbocho street scene is from travel.mynavi.jp.]