A historic rise in soybean prices driven by soaring demand in China is dealing a heavy blow to Japanese makers of traditional staples such as tofu and soy sauce.

Already suffering from falling sales, these manufacturers -- the vast majority of which are mom-and-pop concerns -- find it all but impossible to pass along the higher prices to customers amid the prolonged deflationary trend.

About a month ago, Chuichi Usui saw the price of soybeans rise by 1,000 yen, hitting 7,000 yen per 60-kg sack.