The first sign that something terrible had happened came as a notification on a station platform: my train was running late.

It was a bullet train from Hiroshima to Kyoto. I was travelling through western Japan with friends. I was The Washington Post's Tokyo bureau chief at the time, and I knew enough about my adopted country to realise the bullet trains ran late only when there was a very good reason. I took an escalator down from the train platform.

That's where I saw the television.

It was turned to NHK, the nation's public broadcaster. On the screen, a coastal map of Japan showed red urgent warning signs about a tsunami. Soon, the network, with helicopter footage, was showing the water itself — a wall of blackish-blue fury, ramming into the country's northeastern coast, picking up cars and houses, grinding towns into nothing more than matchsticks.

I gulped and wondered: how many people were in those cars? How many people were in those homes?

It was March 11, 2011, and one of the most powerful and destructive displays of nature in recorded human history was unfolding — a defining moment in postwar Japan. The earth convulsed for a full six minutes. The 9.0-magnitude earthquake actually shoved Japan's main island several feet to the east. The resulting tsunami, 40 feet high in some places, caused a series of nuclear meltdowns and killed 20,000 people. Some bodies were never found.

Beyond even the death and destruction, it was breathtaking to see a country so full of joys and conveniences fall apart so quickly. Almost instantly, the highways were impassible. The cell networks were jammed. The convenience stores didn't have food. The petrol stations didn't have petrol.

As the nation shuttered its reactors, the power supply cratered. The iconic crosswalk in front of Tokyo's Shibuya Station — normally a riot of lights and noise — went dark. The city felt like it had been hit by the world's largest mute button.

As one reactor after the next exploded over several days at the Fukushima Daiichi nuclear power plant, the disaster took on a sci-fi quality. People understood the death, but few could grasp the danger that might be in the air. The Government was cagey about what was going on. Helicopters were dousing the reactors with water in emergency missions. On television, commentators stood over model nuclear reactors, explaining what might be happening, without really knowing. Amid the explosions, people fled the towns around the plant without even packing their bags, and farmers left without releasing their cattle, which later die still attached to their milking stanchions.

Much farther away, in Tokyo, people worried even the capital would become uninhabitable — a realistic fear under the worst-case scenario, as the Prime Minister later revealed.

Then there were aftershocks. Hundreds of them. For weeks. Many nights, after I returned from Hiroshima to Tokyo, my 30th-floor apartment building would be slow-dancing as the ground shook, my closet doors opening and closing.

By midsummer, with so many aspects of life in Japan feeling different, I had moved apartments. The new one was on the second floor.

For the first week or so of the disaster, my job was to "anchor" the daily stories — that is, remain in Tokyo, monitor the news minute-by-minute, talk to Japanese and US officials, and try to make sense of what on earth was happening to the country.

But eventually, I got a chance to head up to the disaster zone, where there were no functioning hotels. I made my way to a particularly gutted city, Ishinomaki, and found a place to stay: with a local college professor who lived on a thimble-like hilltop, one patch of undestroyed land looking out over obliteration. Ostensibly, the professor, Koichi Ohtsu, had also agreed to help me make local contacts for my reporting. But he was a lousy translator. He couldn't stop crying during interviews.

Ohtsu was in his early sixties and lived with his mother, who had Alzheimer's. Every day, as if explaining for the first time, Ohtsu pointed to the TV and told his mother about the peril the country was in. One night, the local news showed footage of the elementary school where Ohtsu's mother once taught. Now it was a blackened skeleton.

"Look, Mom," Ohtsu said. "That is your school."

She covered her mouth.

"Oh, it's a horrible disaster," she said.

I would spend my days out reporting. But what I remember most were the evenings. Ohtsu gave me some blankets and a tatami mat to sleep on, and for more than a week, his home was the bureau. We ate canned whale meat and shared beers after I filed my stories. The city felt like nothing but death and mud. I kept thinking how impossible it seemed, the notion that this place would ever again be worth living in. I kept asking him: What are you going to do? Are you going to stay?

He was adamant that he would. I couldn't figure it out. His college had an uncertain future. He was basically living in the middle of a graveyard.

Although he kept saying how fortunate he was, he didn't seem to believe it. When he would get in his car, he would turn on the Beatles, a little cocoon of joy and normalcy. And then he would see something ghastly — a school bus painted with Pokémon characters jutting from the remains of a kindergarten.

"My God," he would say.

Twice over the past week, I spoke with Ohtsu on Zoom. He warned beforehand that I would see the "wrinkled face of a 73-year-old man". He lives alone now. His mother died seven years ago. He said he tries to keep busy with writing and tai chi, but sometimes he feels lonely.

The first time we talked just to catch up. The second time, Ohtsu prepared a 36-page powerpoint presentation, with before and after photos of his city.

Ohtsu went through slide after slide, which included maps, an overhead view of a memorial site, and the photo of a new Italian restaurant called Trattoria del Centro. His city's recovery had been strange, but mostly complete. What grew back bore little resemblance to what was destroyed. Ishinomaki was now a well-manicured city with wide sidewalks. Several grey high rises had been constructed as permanent new apartments for the thousands who'd lost their homes.

Then he told me about the Wall. It was a massive public works project, a concrete behemoth planted along the coast, designed to stop future tsunamis in their tracks. The wall was grey and controversial, Ohtsu said.

"Unless we go up to the hills, you cannot see the sea," he said.

Ishinomaki had also gotten smaller. Some 3,200 of its 160,000 people died in the tsunami. In the aftermath, 10,000 left and never returned. Another 418 people are still technically categorised as missing. Even ten years later, one day every month, firefighters and police officers fan out across the area looking for bodies.

On the morning of March 12, 2011, Ohtsu had walked to the edge of his snowy hilltop, with a view overlooking the city, and taken a photograph of the destruction: houses smeared into pulp, cars tossed here and there, a ghastly morning-after smoke rising from the scene.

The view now is dramatically different. He sees rebuilt fish-processing facilities. He sees the memorial park, its grass brown in the winter. And, he sees the wall. Ohtsu said he had no regret in staying. The town is livable again. It's not the same city, but it's his city.

He came to the last slide.

It was addressed to me, but it seemed more fitting for anybody who had stuck it out through all the rebuilding.

"Thank you for your kind patience," it said.

• Chico Harlan is The Washington Post's Rome bureau chief. Previously, he was the Post’s East Asia bureau chief, covering the natural and nuclear disasters in Japan and a leadership change in North Korea. He has also been a member of the Post's financial and national enterprise teams