Japan's 40-year government bond yield just smashed through the 4% barrier in mid-January, marking a historic moment—the first time any maturity of Japanese sovereign debt has hit these levels in over three decades. This isn't just a bond market headline; it's a signal about shifting global monetary conditions and capital flows. When JGBs start yielding this much, it reshapes how investors think about safe havens and asset allocation across crypto and traditional markets alike.