Japan and the U.S. threw nearly $100 billion at the yen in July. Two months later, Japan is warning markets again.

The bigger risk is the money that was borrowed in yen and invested somewhere else. If that trade starts unwinding quickly, the selling doesn’t have to stay in Japan.

Japan and the US spent about $80 billion to hold up the yen in July, their first joint intervention since 1998. Two months later the yen is back near 157 and Japan's currency czar is out warning markets again.

When a record check plus Washington's help only buys 2 months, the… pic.twitter.com/2zYRAvlFIB

— Kurt S. Altrichter, CRPS® (@kurtsaltrichter) September 29, 2026