For the first time in recorded history, a single nation counts more than 100,000 living centenarians within its borders — and that nation is Japan. This milestone, reached in 2026, is less a celebration of longevity than a reckoning with time itself: a society that learned to extend life has not yet learned to sustain the structures that surround it. The oldest cohort in human history now presses against systems built for a younger world, asking questions that medicine never had to answer.