“It was like one of the ridiculous scenes from an action movie, except it was real,” said Mr. Miyakawa, his hands quivering. “I was going 70” — kilometers per hour, or about 45 miles per hour — “and the wave was gaining on me. That’s how fast it was.”

When he returned the next morning, he found his home reduced to its foundations, and heard faint cries for help. He followed them to a nearby apartment building, where he found a woman shivering and wet in the March cold and took her to a shelter. “The wave killed many,” he said, “but it spared a few.”

Image Mountains and inlets compounded a tsunami's strength.

Credit... The New York Times

Among them were the town’s children, whose schools were located safely on a hilltop.

In fact, the children said they did not even notice the wave. Ryusei Tsugawara, a 13-year-old middle school student, said he figured something was amiss only when school ended and teachers would not let the children go home. Instead, the children were kept at school until the next day, when his parents and those of some of the other children began to claim them.

Some parents never showed, and the unlucky children have been placed in care of friends and relatives, town officials said. “The town is gone, and I’m scared to stay here,” Ryusei said.

A decision to gather on the roof of the town hall proved fateful for many. Mr. Sato, the mayor, said he and other town employees rushed to watch the approaching wave from the roof, which at three stories high and a half-mile from the shore seemed safely out of harm’s way.

Instead, Mr. Sato said, the water roared up to the building and swept over its roof, pinning him against a steel railing, with his head just above water. He said that was the only reason he survived. Of the 30 people on the roof, only 10 survived by clinging onto the railing or an antenna.