The yen on Monday advanced past the level of 140 against the US dollar, its strongest level since July 2023.
At 5 p.m., the dollar fetched 139.87-88 yen.
The yen had weakened to 160 against the greenback in June.
The Bank of Japan will make an interest rate decision on Friday. It is expected to keep its short-term policy rate target unchanged at 0.25%, having increased rates twice already this year.
Japanese financial markets were closed due to a national holiday.
