A powerful 7.5-magnitude earthquake struck off northern Japan late Monday, injuring at least 33 people and triggering the country’s first-ever “megaquake advisory” along the Nankai Trough. As aftershocks continue and small tsunamis recede, millions from Tokyo to Hokkaido are quietly stocking emergency kits, haunted by memories of 2011 and the knowledge that Japan’s next magnitude-9 disaster may now be weeks—or only days—away.For a nation that has endured the Great Kantō (1923), Kobe (1995), and Tōhoku (2011) catastrophes, Monday’s tremor was both a close call and a wake-up call: the ground beneath the world’s most earthquake-ready country never truly sleeps.