My former British student told me once that she was having trouble finding hard brown bread here. That's true. The types of bread available at most bakeries in Japan are different from what Western people are eating in their home countries. I cannot say which tastes better, Japanese or Western. It is just different, and I like both.
When I was living in Paris, I really loved all types of French bread -- baguettes, croissants and pain au raisin, etc. -- but I sometimes felt like eating softer, sweeter, fluffy Japanese bread. What I missed most was "shokupan," a loaf of simple white bread similar to pain de mie, but bigger and much softer.
It may look like ordinary white bread that you can find anywhere in the world, but...
When I picked up a piece with fingers, it slightly droops due to its softness.
Some people prefer eating "shokupan" with no butter, no jam, even untoasted, so that they can fully enjoy its fluffy texture and subtle sweetness. I can understand them, but I usually toast it lightly, which makes the outside crispy but keeps the inside soft. Ah, it is so yummy.
If you would like to know what a thick and soft Japanese toast tastes like, you should try a "morning set," which normally includes a thick toasted shokupan slice, a boiled egg or a sunny side-up, a drink and sometimes salad. You can order it at many 喫茶店（kissaten) or coffeehouses.
The photo below is a morning set menu offered at 上島珈琲店 Ueshima kohi-ten, a popular café chain located mainly in Tokyo area. Look how thick the bread is! Be careful, the morning set is available only in the morning, till 11 a.m. at Ueshima.
When you buy a loaf of shokupan at a bakery, you can ask them to slice it. If a regular size of loaf is sliced in six, one piece is about 2cm thick.
Today's useful expression: 6まいに きってください。 Rokumai ni kitte kudasai. (Please slice it in six. )
You can replace rokumai (six slices) with the number you like, such as yonmai (four), gomai (five), rokumai (six), jumai (ten) .
*If you have any questions, don't hesitate to email me. Also, I'd appreciated if you correct my English errors. Thank you!