Answer
a high Japanese saving rate relative to Japanese investment
Work Step by Step
Japan runs a trade surplus due to a high level of savings relative to investment. In turn, there is a high net capital outflow, and the outflow is matched by net exports.
The foreign demand for Japanese goods would increase the exchange rate, increasing the demand for Japanese yen. The low demand from Japanese consumers would also increase the exchange rate. Structural barriers against imports would not affect the trade surplus.
