The small factories in the city of Higashiosaka for decades fueled the thundering rise of Japan's biggest brands — but a weak yen and rising costs have accelerated a slow decline, and are reshaping the industrial heartland.

Home to about 6,000 firms, 87% of which have fewer than 20 employees, the city is emblematic of how such forces are pushing Japan's small manufacturers toward a tipping point.

The workshops in Higashiosaka create metal components for everything from train seats to ballpoint pens, and have long relied on powerhouses such as Sharp, Panasonic and Sanyo for orders.