If you’re looking for books in French, you can try the old books markets organized by the Français du Monde association.
1-4-7 Sekiguchi, Bunkyo-ku, Tokyo
4th Sunday each month, except if rainy weather
11am to 5pm
Institut français market
8 Izumidono-cho Yoshida Sakyo-ku Kyoto One Sunday a month (irregular Sunday)
10am to 4pm
I attended the first old books market held in Nagoya (with support of the Français du Monde association) last Sunday and it was a success so they plan to organize another one for September 2023.
More info on their socials
Don’t hesitate to comment if you have questions ^^
Pictures of the old books market last Sunday in Nagoya
* my haul😅