For the first time in a generation, Japan's central bank has raised its benchmark interest rate to a 31-year high, moving at a pace of tightening not seen since 1990. The Bank of Japan, long a guardian of near-zero rates born from decades of deflation and stagnation, has concluded that the inflation now coursing through the economy demands a different posture. This is a quiet but consequential turning point — not merely a policy adjustment, but a signal that Japan's long economic winter may be giving way to a more volatile, and more uncertain, season.