This post is part of a series about the differences in ingredients between Japan and the U.S. When I first arrived in Japan, I had a lot of trouble at times because I wasn’t used to these differences, so hopefully this information is helpful! For the full list of posts in this series, see this page.
In America, I used all-purpose flour for everything. I’ve heard that something similar – 中力粉 (chuurikiko) exists in Japan, but I’ve never actually seen it in the grocery store. Instead, I see two main varieties of wheat flour: 薄力粉 (hakurikiko) and 強力粉 (kyourikiko). The first is something like cake flour in America. This should be used for cakes and cookies. The second is like bread flour, and should be used for more bread-like baking. Here are the types of flour and their gluten contents, according to Wikipedia and Wikipedia Japan:
Bread flour 10-13% 強力粉 （きょうりきこ） >12%
All-purpose 9-12% 中力粉 （ちゅうりきこ） ~9%
Cake flour 8-10% 薄力粉 （はくりきこ） <8.5%
“Weak flour” (薄力粉) is significantly cheaper than “strong flour” (強力粉), but it will not make successful bread, so I usually keep both on hand.
When using American recipes that call for all-purpose flour, I generally make a 50-50 mixture of the strong and weak flours. When making bread I use strong flour. I also find that I sometimes need to increase the amount of flour. An important point to remember is that strong flour adds structure, so if your cookies are coming out too flat, or your dough is too sticky, add more strong flour.
Whole-wheat flour is called 全粒粉 (zenryuufun) in Japanese. In the past few years, I’ve seen more products made with alternative flours like whole wheat or rye, but still have not often seen the actual flour sold in the grocery store. They are available at specialty or import stores, but I think your best bet is to order them online.
I’ve seen rice flour (米粉, komeko) at the supermarket on occasion as well, and there are some other flours that are sold for specialty use, such as roasted soybean flour (きなこ, kinako) and glutinous rice flour (もちこ, mochiko) which are mainly used for making traditional Japanese sweets.
Otherwise, non-wheat thickeners such as cornstarch (コーンスターチ, kounsutaachi) and potato starch (片栗粉, katakuriko) are widely available as well.