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On the evening of 15 June 1896, the lunar Boys' Festival, Sanriku villagers felt only weak earthquake tremors and stayed home celebrating. Roughly half an hour later, waves reported at over 30 meters in places struck the coast and killed about 22,000 people. Because the shaking was mild, almost no one fled, and whole hamlets were erased in minutes.
After 1896, several villages moved homes to higher ground. Over the following decades, people returned to the shoreline because fishing work, boats and daily convenience pulled them there, and as survivors aged, the fear of the sea no longer outweighed that pull. When the 1933 Shōwa tsunami came 37 years later, it killed about 3,000 people, many in the same low sites that had been abandoned once and then resettled.
The records and testimonies describe warning signs before the waves: wells drying or clouding, unusual catches of fish, and booming sounds offshore. Villagers had these observations, but they judged danger by how hard the ground shook, so the signals that did not fit that measure were ignored. On this view, disasters are less often unforeseeable than unrecognized, because people read evidence through the wrong indicator.
Yoshimura rebuilds both catastrophes from village logs, eyewitness interviews, and schoolchildren's compositions written just after 1933. The book treats these documents as a practical warning system that holds concrete, local knowledge of where the water reached and who lived.