I’ve lived off and on in Japan since the 1970s, in various places. Most recently I’ve lived in Kyoto. The longest place I’ve ever lived is Tokyo. I think the shoe situation in Japan has changed in the last few decades, as Japanese people have gotten larger over the years, but when I first began traveling to Japan, it was impossible to find my shoe size.
Once, in 1976, while I lived in Fukuoka, I decided I needed running shoes. I went to the local sporting goods stores and asked to try on a pair. The clerk bought me the largest size they had for women. I think they were 24.5 cm, around a 7.5 in America. At that point I wore an 8.5, even a 9.