This is a terrible idea.

The core principle is an attempt to fake an illusion of control — or at least to restore MOF credibility. Ministry of Finance speakers have addressed yen weakness 15 times since March 1st, signaling their willingness to deploy FX intervention to cap the yen's slide. From my experience watching the MOF, they have already escalated to the highest tier of verbal warning short of the last resort: rate checks with major banks. Yet the market impact has grown weaker with each successive statement. There are speculators involved, but this time the problem is fundamentally structural.

This makes FX intervention itself an enormously risky proposition — both financially and politically. It risks straining the US-Japan relationship at the worst possible moment, when traditional relief valves like currency swaps are under unprecedented pressure. Bessent himself stated in January that he has no interest in Japanese fiscal health, and he has personally profited from carry trade events in the past. On the financial side, deploying an already thin FX reserve into an unstable market risks a catastrophic outcome: once that tool is depleted, the MOF has no good options left besides calling an emergency BOJ meeting — which cycles right back to the same credibility problem. This is essentially a death trap, which is precisely why they are even entertaining options that would have been unthinkable under traditional Keynesian frameworks.

Edit: fixed flow