When the earthquake struck, exactly one year ago, at 2.46pm on March 11, 2011, Sasaki Hideharu knew exactly what to do.
The reserved but capable 39- year-old waited for the ground to stop shaking and then dashed up the staircase outside his workplace, the sports centre in the town of Rikuzentakata. The two-storey building had been designated as one of the town's tsunami evacuation centres and Mr Sasaki knew that a wave was on its way, and that people would soon start filing in from the houses nearby.
"I was looking for a radio, so I could find out how big the tsunami would be," he said. "When I found one, the reports said Miyagi would be struck by a six-metre wave, so I thought it would be the same here."
Actually the tsunami was 46ft high when it washed into Rikuzentakata, up to the roof of the sports centre.
That mistake cost the lives of everyone he helped to usher into the building, between 80 and 100 people, he estimates. Only four people, including himself, managed to survive.
Tomorrow, as Rikuzentakata gathers to remember the disaster, he will not be attending. "I want to visit the families of my friends who died. But I am not sure if that would be the right thing to do."
Standing outside the wrecked sports centre, he said the fear "never entered" his mind that it would not be a safe place to shelter. Today the centre is a desolate sight, one of the few buildings in a plain where houses once stood. Its face has been ripped off, leaving girders and wires dangling. Inside, there is sand on every surface. The back wall was punched through by the force of the tsunami and there is still an upturned car in the middle of the wooden floor.
"As the people made their way here, I told them all to go up the outside staircase to the second floor. We had about half an hour from the earthquake to get everyone up. I was at the top of the staircase helping the disabled, people in wheelchairs, the older people," he said.
Then he looked up at the sea. "First I saw the water coming through a line of pine trees near the bay. Then I saw it reach the houses. Then I saw the houses moving towards us," he said. "It was not an angry wave, it looked quite unthreatening. It just slowly crept up. And then suddenly it was there, an enormous mass of water. When I saw the houses being swept towards us, I realised suddenly we might not be safe. Then people started to panic and to run away from the water, towards the back of the hall where there are lavatories. But I knew we would be trapped."
By the time that Mr Sasaki realised the evacuees had made a mistake, the water was up to his knees.
"I reached the lavatories at the back and turned around. I saw the huge plate glass window at the front of the hall shatter and a wave of water rush in," he said. Then, in a split second, his head was underwater. "I gasped, and inhaled a mouthful of seawater. I started to choke, to panic, and immediately I thought this was the end. But then, as images of my three children flashed before me, I became determined I would not die that day."
He scrabbled to get a grip. Finally, as his body rose, he managed to hold on to a pipe.
"I could feel other hands brushing my body. There were people all around. I grabbed one hand and tugged hard, trying to bring it up with me, but it slipped out of my grip."
As the water rose, he was able to find an air pocket. For the next 10 minutes, he rose and fell, searching for mouthfuls of oxygen. Finally the water began to fall, little by little.
After he finally fell to the floor, he searched for a child's voice he had heard crying out. It turned out to be a woman, Yoshida Chikako, who had been shouting out for her husband as he slipped away from her. Together with a third survivor, they waited out the first night, shivering in wet clothes.
"In the other bathroom, there were about 10 bodies. In the hall, people had got caught in the beams. "
Mr Sasaki said he had tried to exorcise his demons by throwing himself into emergency work, delivering aid to those left homeless, and by visiting families of victims who died in the sports centre.
"If the radio had said the wave would be 10 metres, instead of six, I am sure that someone would have suggested we move everyone elsewhere. Maybe I would have suggested it." (© Daily Telegraph, London)