European-style bread is ubiquitous in Japan now, but was bread, or other wheat products, a significant part of the Japanese diet before European interaction? If so, how was it used? Chinese cuisine features breads like the mantau or the pau, but there doesn't seem to be an equivalent in Japanese food. Why did Japan not adopt Chinese-style bread?
Please see this thread. Non-rice grain was extremely important part of the pre- and early-modern diet. This is especially true in the countryside. Multiple sources report that most rice were either given to the authority for taxes or sold for money to pay for other things (the rice itself was mainly consumed in the cities), and for rural people non-rice grains made up most of their diet.
Besides porridge and steamed mixed-grain, food made up of milled powders were popular as well: your soba, udon, sōmen. And yes, the Japanese did import the mantou/bao from China. It's called manjū. There's even a shrine honouring its supposed introduction in the early Muromachi period.