Whole-wheat and whole-grain products are hard to find in Japan, where most bakeries and supermarkets sell white bread products only.
Of the three major bread manufacturers in Japan, only Shikishima Baking Co.'s Pasco brand offers loaves of bread and "English" muffins made from whole-wheat flour — it's called the Mugino Megumi (The Blessings of Wheat) series.
According to the company, the amount of dietary fiber contained per slice of a loaf of Mugino Megumi whole-wheat bread is 2.3-3.6 grams, depending on how thick the slice is. Pasco also has a rye bread series, but the amounts of fiber are not listed on their nutrition facts labels.
If you have time to search, you can find some small, specialty bakery shops that sell bread made of domestic whole-wheat flour and natural yeast. Compared to the supermarket, though, the prices are likely to be steep.
What you can find easily in Japan, instead, are a range of unmilled or partially milled rice products. In addition to genmai (brown rice), you often see hatsuga-genmai (sprouted brown rice) and haigamai (rice without embryo buds) at major retailers. Mini-packets of zakkoku (millets), which you can mix with rice before turning the cooker on, are also popular. These are all richer in fiber, vitamins and minerals than white rice.
According to the e-healthnet, a health information website run by the Health, Labor and Welfare Ministry (www.e-healthnet.mhlw.go.jp), other common Japanese foods that contain dietary fiber include takenoko (bamboo shoot), gobō (burdock), satsumaimo (sweet potato), fuki (butterbur), hijiki (a kind of brown, edible seaweed), kanpyō (dried gourd shavings) and kiriboshi daikon (dried strips of radish).