It was an email from an old friend that led me to the irradiated sunflower fields of Fukushima. I had not heard from Reiko-san since 2003, when I left my post as the Guardian's Tokyo correspondent. Before that, the magazine editor had been the source of many astute comments about social trends in Japan. In April, she contacted me out of the blue. I was pleased at first, then worried.

Reiko's message began in traditional Japanese style with a reference to the season and her state of mind. The eloquence was typical. The tone unusually disturbing: "It is spring time now in Tokyo and the cherry blossoms are in bloom. In my small terrace garden, the plants – tulips, roses and strawberries – are telling me that a new season has arrived. But somehow, they make me sad because I know that they are not the same as last year. They are all contaminated."

Reiko went on to describe how everything had changed in the wake of the nuclear accident in Fukushima the previous month. Daily life felt like science fiction. She always wore a mask and carried an umbrella to protect against black rain. Every conversation was about the state of the reactors. In the supermarket, where she used to shop for fresh produce, she now looked for cooked food – "the older, the safer now". She expressed fears for her son, anger at the government and deep distrust of the reassuring voices she was hearing in the traditional media. "We are misinformed. We are misinformed," she repeated. "Our problem is in society. We have to fight against it. And it seems as hard as the fight against those reactors."

She urged me to return and report on the story. Five months on, that is what I have tried to do. Driving around Fukushima's contaminated cities, Iwate's devastated coastlines and talking to evacuees in Tokyo, I've rarely felt such responsibility in writing a story. Reiko and other Japanese friends seemed to be looking not only for coverage, but for an outsider's judgment on the big question weighing on their minds: is Japan still a safe country?

The magnitude 9 earthquake that struck Japan on 11 March was one of the five most powerful shocks recorded; so powerful that it lowered the coastline by a metre and nudged Japan two metres closer to the United States. It was followed by a devastating tsunami – which rose to a peak of 40m – and accounted for most of the destruction. These two natural catastrophes left 20,000 people dead or missing and 125,000 buildings destroyed. They triggered a third disaster – the multiple meltdown of three reactors at the Fukushima Daiichi nuclear plant that have together released more radiation than any accident since Chernobyl. Such was the magnitude of the catastrophe that Emperor Akihito delivered a televised address to his people. The almost archaically formal speech was so rare that it was compared to the historic radio broadcast by his father, Hirohito, that announced Japan's surrender after the atomic bombing of Hiroshima and Nagasaki in August 1945 – and prompted an era of national reform and rebuilding. Six months on, the emergency is over. But another disaster is becoming apparent: a psychological crisis of doubt and depression that could prove more destabilising than anything that came before.

The streets are clear of debris, reconstruction is under way and evacuees are moving out of shelters. But millions of people are having to readjust to levels of ionising radiation that were – until March – considered abnormal. This is not a one-off freak event, it is a shift in day-to-day life that changes the meaning of "ordinary". But quite how is hard to determine. Low-level radiation is an invisible threat that breaks DNA strands with results that do not become apparent for years or decades. Though the vast majority of people remain completely unaffected throughout their lives, others develop cancer. Not knowing who will be affected and when is deeply unsettling.

This has happened before, of course. Twenty years after the 1986 reactor explosion in Chernobyl, the World Health Organisation said psychological distress was the largest public health problem unleashed by the accident: "Populations in the affected areas exhibit strongly negative attitudes in self-assessments of health and wellbeing and a strong sense of lack of control over their own lives. Associated with these perceptions is an exaggerated sense of the dangers to health of exposure to radiation." Russian doctors have said survivors were "poisoned by information". But in Japan, it would be more accurate to say that people are contaminated by uncertainty.

On my first morning in Fukushima, I was shaken awake by a magnitude 6 earthquake, one of the many hefty aftershocks that have wobbled eastern Japan since March. But that is not what plays most on the mind. Japan's population is accustomed to physical instability. This is, after all, the most seismically active nation on earth. For centuries, the nation's culture has been infused by a spirit of "mujo", or impermanence. It is at the core of the nation's identity and – until now – its resilience.

But this disaster is different. In a country long famous for safety, hygiene and raw food, millions of people are now being asked to accept a small but persistently higher health risk, long-term contamination of their homes, gardens, streets and schools; and food that is now deemed safer if it is prepackaged and from as far away from Fukushima as possible.

In other countries, people might want to put more distance between themselves and the source of the radiation, but this is difficult on a crowded archipelago with a rigid job market. Thousands have fled nonetheless, but most people in the disaster area will have to stay and adjust. Doing so would be easier if there were clear guidance from scientists and politicians, but here, too, contemporary Japan seems particularly vulnerable. The country has just got its seventh prime minister in five years. Academia and the media have been tainted by the powerful influence of the nuclear industry. As a result, a notoriously conformist nation is suddenly unsure what to conform to.

Sachiko Masuyama, 29, in her new appartment in Tokyo on the 29th floor. She escaped from her house in Minami-Soma (Fukushima prefecture), 25km from the nuclear power plant, in May. She took refuge in a public housing unit in Tokyo with her two children and her husband. She is pregnant and will give birth in November. Photograph: Jeremie Souteyrat

"Individuals are being forced to make decisions about what is safe to eat and where is safe to live, because the government is not telling them – Japanese people are not good at that," says Satoshi Takahashi, one of Japan's leading clinical psychologists. He predicts the mental fallout of the Fukushima meltdown will be worse than the physical impact.

Unlike an earthquake, he says, the survivors do not suffer post-traumatic stress symptoms of insomnia, shaking and flashbacks. Instead, the radiation "creates a slow, creeping, invisible pressure" that can lead to prolonged depression. "Some people say they want to die. Others become more dependent on alcohol. Many more complain of listlessness."

Sachiko Masuyama has suffered many of these symptoms as she has been forced to make life-or-death decisions for herself and her unborn baby. On 9 March, she found out she was expecting her third child. Two days later, the Fukushima Daiichi nuclear plant – only 25km from her home – was jolted into meltdown. And since then her life has been turned upside down, first by a desperate escape from the disaster zone, then by a growing worry about the effects of the radiation on the foetus growing inside her.

Each time she goes to the hospital for a checkup, she is filled with anxiety that the ultrasound might reveal a deformity, so she counts and recounts the fingers and toes. The doctors have reassured her there is no sign of abnormality, but they won't know for sure until the birth in November – and perhaps not for years later. For Masuyama, the worry has become so all-consuming that she has considered abortion and suicide.

"For the first two months after the disaster, I was focused only on survival," the 29-year-old tells me in a Tokyo restaurant, "but since then I have had time to think and that has made me very depressed. I have been so worried that I stopped eating. I wanted to die."

There is nobody nearby to confide in. Her friends are scattered across refuge centres in Japan. Her in-laws want her to return because the government and the power company say it is safe. But they have withheld so much information since the disaster that she no longer trusts them.

"When I watch the documentaries about Chernobyl, it is horrifying, but I have decided to give birth," she tells me. "I have three children: one inside me and two outside. I wouldn't kill my son and daughter because they were exposed, so how could I kill my unborn child?"

She'd like to return to her former life, but her home, Minami Soma, is in the midst of a major decontamination operation: the streets are being cleaned, every surface sprayed. Instead, she's chosen to remain in Tokyo, where she feels lonely but safe. The decision has not been easy. "I don't like it, but I have to choose. We Japanese like to follow each other, but this time it doesn't seem right."

Did she need to leave? Travel around Fukushima today and there is little evidence of disaster or trauma. In the cities, the streets throng with smart suited salarymen and office ladies. In the countryside, the paddy fields are heavy with rice. Watch the bullet train speed through a frame of distant mountains and sharp blue skies and this seems to be postcard-perfect Japan.

But look more closely and you will see that many families now own Geiger counters or dosimeters to check their exposure. DVD chain stores have started to rent them along with the latest Hollywood blockbusters. Inside hundreds of school playgrounds, bulldozers are scraping off the top 50cm of dirt to reduce contamination from the soil. Local newspapers and TV bulletins carry daily radiation updates with a breakdown for every neighbourhood.

Zen monk Koyu Abe lets people dump contaminated soil from their gardens on the hillside behind his temple. Photograph: Jeremie Souteyrat

Each day for most of the past six months, there has been a steady drip, drip, drip of worrying news: cesium found in the breast milk of seven mothers; strontium discovered inside the city limits; 45% of children in one survey testing positive for thyroid exposure. There are reports of suicides by desperate farmers and lonely evacuees, contaminated beef smuggled on to the market, and warnings that this autumn's rice crop may have to be abandoned.

At the Koriyama Big Pallette – a conference centre-turned-refugee shelter – in southern Fukushima, most people have moved into temporary shelters. The few that remain benefit from ample provisions, friendly volunteers and cardboard-and-curtain partitions designed by the world-famous architect, Shigeru Ban. But an electronic display inside the corridors shows a reading of 0.1 microsieverts (becquerels, the quantitative measure of radiation, are converted to sieverts to offer a qualitative indicator of the impact on the body). The question of whether it will return to normal prompts a sigh from volunteer Michio Terashima. "Normal no longer means what it did. The nuclear disaster didn't turn out to be the cataclysm we feared at first and many things are getting better, but they will never be the same again."

But there's also an effort to decontaminate and lift spirits. Fukushima is distributing 20m sunflower seeds to suck up the cesium radionuclides that have permeated the soil. The towering yellow flowers now adorn gardens, farm fields and roadside plots. Although they brighten the landscape, their stalks and petals concentrate the radioactivity and will later have to be burned or left to decompose in a controlled environment.

The sunflowers are the brainchild of Kouyuu Abe, a Zen monk who owns a temple just outside Fukushima city and is committed to the "fight against radiation". He allows people to dump the irradiated soil from their gardens on the hillside behind his temple, where it will be buried and covered with zeolite. He is also planning to decontaminate the forests with high pressure sprays so the leaves are less of a hazard when they fall in the autumn.

His greatest concern is the mental wellbeing of his followers. "There is a lot of information but huge uncertainty. That makes everyone uneasy. The politicians, bureaucrats and academics cannot agree on anything, so how can people feel reassured? We need positive action, but we don't know what to believe."

Many locals are farmers, who are despairing about their contaminated soil. "Young people are leaving. In the past six months, there has been an increase in suicides. There will be more. If you don't give people hope, they lose their reason for living."

Adding to the problem is a trust deficit. Ministers have admitted holding back vital information in order to prevent a panic. Government spokesmen initially denied there was a meltdown and said the plant's problems posed "no immediate risk" to human health. Safety authorities ranked the accident as a mere four on the international scale of nuclear accidents. Not until a month later did it upgrade this to a maximum seven – like Chernobyl. The full details of what happened to the nuclear reactor are still emerging and far from complete.

The day after the earthquake, there was an explosion in the No 1 reactor building. Two days later, the No 3 reactor building blew its top. The following morning there were blasts at reactors two and four. These explosions released a plume of radiation, but the government withheld projections of its size and how it spread up and down the coast and inland to Fukushima city, Koriyama and Tokyo.

Nuclear and emergency workers were also in the dark. I drive to Iwaki, a coastal city south of the power plant, to interview one of the men involved in the clear-up operation. T-san was evacuated from Fukushima Daiichi plant after the earthquake struck and returned almost two weeks later to join the containment operation.

"They didn't tell us anything," says T-san, who has asked to remain anonymous. "Nobody mentioned a meltdown. We didn't get any critical accident training or instructions. But we all knew the situation was very bad. I thought this might be my final mission. I know it sounds a little silly, but I felt like a kamikaze who was prepared to sacrifice everything for my family and my country."

Since March, he estimates he has been exposed to 50 millisieverts of radiation. Under the government's previous guidelines, this was the maximum allowed for an entire year.

He is not alone. By Tokyo Electric's own figures, 410 workers have, like T-san, been exposed to more than 50 millisieverts since the disaster. Another six have received a dose above 250. But in an emergency move, that became legal in March, the government has increased the permissible dose for nuclear workers from 100 to 250 millisieverts.

"They changed it so suddenly and dramatically that we didn't know what was dangerous, what was safe," T-san says. "We were confused. Had the government been too strict before, or was it suddenly being too lax? We didn't know what to believe."

It is a common refrain. Since March, the government has relaxed radiation targets for food, nuclear workers, school playgrounds and discharges into the sea. What was considered dangerous a year ago is now deemed safe and legal. Close to 2 million people in Fukushima are living in areas where the annual radiation dose exceeds the one millisievert per year safety target set by the government for the general population. Even in downtown Tokyo – 240km from the reactor – levels have risen close to the point where they would have to be marked with a "Radiation Hazard" warning if they were found in a workplace.

According to the WHO, the average background radiation people are exposed to worldwide is 2.4 millisieverts per year [see footnote]. A single chest x-ray adds 0.1 millisieverts, a six-hour transatlantic flight 0.5 and a whole-body CT scan 12 millisieverts. However, in these cases, the radiation is predictable, external and relatively easy to deal with. The fallout from Fukushima was far messier and likely to enter human bodies, where radiation does more damage.

Supermarket signs declaring radiation safety. Many prefer to place their trust in imported foods. Photograph: Jeremie Souteyrat

After the explosions, the radionuclides scattered like the debris from a firework display, according to wind direction and the weight of the particles. Each has a different impact on the body. First and farthest to spread was gas-light iodine 131, which tends to accumulate in the thyroid gland – it was quickly detected as far away as Tokyo. Next came particles of cesium 134 and 137, which affects the bladder and liver with a half-life of about 30 years – this contaminated the soil, water and trees of most of Fukushima as well as chunks of Miyagi, Chiba and Tokyo and remains the biggest problem. Strontium, which tends to accumulate in the bones and causes leukaemia, is spread less widely, but it has been found in 64 locations, including Fukushima city. The heaviest radionuclide, plutonium – with a half-life of tens of thousands of years – has been detected in small quantities inside the plant perimeter and may have been leaked or discharged into the Pacific Ocean along with more than 10,000 tonnes of heavily contaminated water.

The overall radiation release from the plant is staggering – 770,000 terabecquerels in the wake of the accident and a billion becquerels still being added each day while engineers struggle to seal the broken containment structure. Most of the iodine – with its eight-day half-life – has since decayed and the cesium and other radionuclides have been diluted and dissipated. But much has seeped into the soil, contaminated the leaves in the forests and is being passed through the food chain to cattle, fish, vegetables – and humans. As more details become apparent, people in Fukushima are trying to work out what dose they have received. They look back at where they were on the peak day of 15 March and calculate how long they were outside, whether it was snowing and what they were wearing. Then they consider what they have eaten and drunk since and whether it was from a safe source.

There is not much they can do about it. Full-body scans – promised by the government – will take time. Checking the radiation in every item of food is almost impossible, but one group is trying to help out. The Citizen's Radiation Monitoring Station in Fukushima – which has been set up by the journalist Ryuichi Hirokawa – offers free grocery checks. It is a slow process. Each item must be peeled, ground or grated, bagged and then placed in an LB 200 Becquerel Monitor for 20 minutes.

Akiko Sakuma drove from two hours away to test the potatoes in her allotment. "It's terrifying. I think about the radiation every day," she says and shows me a notebook in which she meticulously records the doses to which she is exposed. When it snowed after the explosion on 15 March, the level was over 100 microsieverts per hour – equivalent to 1 x-ray. She said she suffered headaches and nosebleeds. "I want to run away to Tokyo, but there is no work. I could never understand why people in Chernobyl didn't flee, but now I'm in the same situation."

Yet it is also not hard to find people who are fatalistic. Several tell me there is a greater risk from stress and upheaval than from the radiation. The divergence of opinion has led to divisions among families, generations and communities. "Should I stay or should I go?" is a question that weighs heavy on countless minds. It is why hotels in north-eastern Japan are struggling to attract tourists. It explains the rash of postponed visits by foreign dignitaries to Tokyo. And it is a particular worry for those whose DNA is most vulnerable to change: expectant mothers and young children.

Among them is Mari Ishimori, another pregnant evacuee in Tokyo, who is struggling to balance health concerns for her unborn baby and pressure from her in-laws to return to her husband in Fukushima. It is a conservative rural area, but many wives, she said, are now arguing with their husbands.

As soon as she heard about the accident at the plant, she fled. "I love my husband, but I will never return to Fukushima," she says over a coffee. "I want my child to have a normal childhood. But if we are in Fukushima, I will have to say, 'You can't touch the ground or touch the leaves or go in the river.' I want my child to grow up without worrying about that, just as I did. That's hard. I'm not sure if my husband and I will live together again."

Ishimori has more reason than most to fear radiation. She grew up in Hiroshima, the city that was the target of the world's first atomic bombing. During her childhood, her grandmother and great-grandfather recounted the horrors of the US attack and the fallout that followed. She has seen the prejudice suffered by "hibakusha" – nuclear survivors – whose children are sometimes treated as though they bear the contamination in their genes. The discrimination is well documented. Some are refused employment. Others are rejected as marriage partners because of medically unproven fears that their offspring may be born with deformities. But the hibakusha are also revered as survivors and repositories of knowledge about the very real risks or radiation. After the disaster, they were among the first to demand a greater sense of crisis even as the government was offering soothingly ambiguous words about there being "no immediate health impact".

Due to give birth next month, Ishimori is now alone. She avoids eating fish, meat or eggs, and is deeply sceptical about official safety assurances. "I don't trust anything they say. Tokyo Electric and the government have told us so many lies."

Behind much of the anxiety and suspicion is a lack of clear guidance about the health risks. But the fact is that no one is capable of setting a totally safe level of radiation. Masao Tomonaga, the director of (Japan Red Cross) Atomic Bomb Hospital, has been studying the effects of radiation for 40 years. Based on the survivors of the US atomic bombings of Hiroshima and Nagasaki, he has proven that for every rise above 100 millisieverts of radiation exposure, there is a corresponding increase in the likelihood of cancer. It is assumed the same linear pattern applies at lower levels, but the change is too small to measure with accuracy.

"We cannot give people data to prove that five millisieverts is very safe or 10 is very safe. There is no clear evidence," Tomonaga says. "With the atomic bombs, the survivors received a massive dose of radiation over their entire bodies in a short space of time. In Fukushima, people are getting a very small dose every day. This is an important difference."

Chernobyl offers a closer comparison. The accident in the former Soviet Union left 134 cleanup workers with acute radiation sickness. Twenty-eight died within a year. Millions more were exposed to lower doses and a wide area of Belarus and northern Europe was contaminated. In a follow-up study 20 years later, the WHO concluded the accident caused an additional 4,000 cancer deaths – about 4% higher than the normal rate – among the 626,000 most highly exposed people. For those exposed to lower levels of radiation, it estimated that cancer fatalities would rise by about 0.6%. The organisation also noted Russian studies showing increased risk of heart disease and cataracts, but it found no evidence of an impact on fertility, miscarriages or birth defects.

Given that Fukushima has released a tenth of the radiation of Chernobyl and taken greater steps to prevent contamination through milk, this would suggest Japan must brace for hundreds – rather than thousands – of extra cancer cases and births may not be as much of a problem as many believe.

That ought to ease the minds of expectant mothers like Masuyama and Ishimori, but they – like many in Japan – are sceptical of official reassurances. They are aware of alternative studies of Chernobyl, which suggest the number of extra cancer cases caused could be 30,000 to 900,000. They know, too, that population densities in Japan are 10 times higher than in Belarus. There are suspicions that politicians put economic cost above public health when they withheld projections about the spread of radiation. In Namie – the worst-affected area outside the exclusion zone with readings 200 times the permissible level – locals have described this as "murder". There is also a growing awareness of the influence of the nuclear industry, particularly Tokyo Electric, which is one of the country's biggest advertisers, campaign donors and science graduate employers.

Watching the obfuscation by Tokyo Electric and the slow response of the government, some people have become depressed. Others have been radicalised.

Ryuichi Hirokawa, a photojournalist, covered Chernobyl and was one of the first reporters independently to measure radiation near the Fukushima nuclear plant after this year's accident. He believes the industry is once again in the process of a cover-up because the investigation into the health impacts of the disaster is being led by academics who, he says, have long served as cheerleaders for the power companies.

"These are the same people who initially said there was no impact from the Chernobyl accident," the veteran reporter tells me in his Tokyo office. "They treat people like guinea pigs. They collect information, but they don't share it with the individuals. There will be no results and no treatment."

To counter this threat, he's raised money to buy advanced monitoring devices – including ¥3.5m (£28,000) whole-body monitoring devices – that are being used for free at the citizen centres. "I am worried about the government's health survey," he says. "That is why I have provided these machines. They want as few people to be recognised as radiation victims as possible. We have to fight that with information. That way we can ensure people are better aware of the risks and they can get the medical treatment they need."

Some see this new questioning of authority as a chance to shift industrial and political baselines for the better. Tetsunari Iida is a former nuclear engineer who has been advocating a shift towards solar, wind and geothermal for more than a decade. His Institute for Sustainable Energy Policies was marginalised until 11 March, but after the meltdown, Iida's call for nuclear power to be phased out has gained traction. Opinion polls suggest 70% of the public support the idea.

Iida is now working with Masayoshi Son – the founder of SoftBank and one of the country's most respected entrepreneurs – to generate more funds for clean energy. This week they will launch the Japan Renewable Energy Foundation in which Sun has promised to invest a billion yen. Businessmen, politicians and celebrities are more critical of the nuclear industry, which would once have been career suicide, and the country's top news programme has stopped taking sponsorship from the power company.

The shift has been noted in Nagatacho, Tokyo's political heartland. After Chernobyl, the Soviet edifice collapsed within five years. The main parties are calculating how far they must change to avoid a similar fate. Former prime minister Naoto Kan called for an end to the use of nuclear power in Japan – and promptly lost his job. His replacement, Yoshihiko Noda, is far more cautious, suggesting the momentum for change is slowing. Even the Liberal Democratic party – which gets much of its funds from the industry – is promising to reduce the country's reliance on this energy source. But for anyone to do that, they will first have to regain public confidence.

I meet the politician charged with rebuilding the disaster area – reconstruction minister Tatsuo Hirano – and ask what needs to be done to restore trust.

"Until now, we have tried to help people who have been directly impacted by the disaster," he says, "but we must also help those who are having to live for the first time with radiation." The government has earmarked ¥23 trillion (£181bn) for reconstruction over the next 10 years, but it has yet to calculate the cost of the radiation clear-up. That is partly because the full extent remains unknown.

To relieve public anxiety, Hirano – who is from the disaster area – says the government must find out whether it was the earthquake or the tsunami that destroyed the reactor's cooling systems and clear up other remaining mysteries. It has launched a detailed study of the radiation inside the 20km exclusion zone, a long-term programme of health checks for Fukushima residents, and established an expert panel to set definitive radiation standards. A food safety commission recently proposed a new lifetime maximum radiation dose for Japanese citizens of 100 millisieverts, excluding natural background and medical radiation.

Masami Takano’s mother watches as he leaves for Shiga, 450km away. 'I’m running away,' he says. Photograph: Jeremie Souteyrat

Ultimately, he would like to see a restructuring of the power industry, including the steady phasing out of Japan's 54 reactors, starting with the oldest first. The nuclear industry is certain to put up a fight, but Hirano predicts voters will insist on change. "In the next election, politicians will not be elected if they support nuclear expansion in exchange for personal benefit."

But does Japan have the dynamism to denuclearise, decontaminate and regain confidence? The country has bounced back in the past, but this time it has a shrinking, ageing population, an economy in the doldrums and a putrid political system. A new start will be difficult, but some are already making a move.

On my final day in Fukushima, I wake up at 5am on a drizzly morning to see off Masami Takano, who is leaving his home of 30 years and his job as a chef.

He wants to leave early as he has a 10-hour drive to Shiga, a mountainous prefecture on the other side of the country, where he plans to make a new life far from the radiation leak. As his mother sobs, he packs his Honda with boxes of clothes, the noodle-making equipment he will use to find a job and a few Lady Gaga CDs for the journey.

He has already bid farewell to his friends: "I told them straight: 'I'm worried about radiation so I'm running away.' Some of them disagree. I understand, it's difficult to leave – I have been here almost all my life – but it's not safe here."

The government, meanwhile, is urging evacuees to return. Officials insists the area is safe. Radiation levels have fallen in the past two months from 1.2 to 0.7 microsieverts per hour. But there is still concern about food and Takano is taking no chances. "Moving will be stressful, but at least I won't have to wear a mask or fear that I am being exposed to more radiation every day."

Over a final cup of coffee, he watches the morning news. The top story reveals that radiation inside the nuclear plant is still at a lethal level of 10 sieverts per hour. This is followed by an item on a nuclear cover-up by Kyushu Electric.

"Nowhere is completely safe," Takano says. "Japan is not a big country, but we have so many reactors. There is a power plant near my new home. I want to tell the local people what a risk they are taking," he says. "My internal organs have been irradiated. That will continue to affect me for many years. So even after I move, the worry won't completely go."

It is time to leave. He gets into the car and, as his mother and their elderly neighbour Sato-san look on, he motors down the narrow driveway, past the cracks caused by the earthquake. As the car turns out of view, his mother is red-eyed and speechless. Sato-san seems unsure what to say.

"He's gone," she starts, then changes the subject to her garden. "Look at these sunflowers. I planted them to soak up the cesium. I can't believe how big they have grown."

Before publication, I sent Reiko a draft of this article. Her reply was polite, but I felt she was disappointed. "Maybe you can find the answer. Maybe it is too much to ask. If so, just forget it. Even though I am much louder than other Japanese, I feel I am lost. My life here requires me to be normalised, to behave like we used to. I have to work, I have to eat. After five months of struggling, I am getting tired of worrying. It is much easier to give up pursuing reality. What bothers me most is being torn in this conflicting situation with no answer, every moment."

I sympathise immensely but regret that I cannot offer the comfort of clarity. The nuclear disaster has been terrifying, but not as expected. If someone had told me a year ago that three reactors would melt down simultaneously, I would have assumed an apocalypse. Yet Japan today is not like any doomsday I imagined. Instead, there is a kind of slow decay. After three visits to Fukushima, I am less afraid of radiation than I was a year ago but more worried about Japan.

• This article was amended on 14 September 2011 to correct a number of errors. References to the amount of radiation a person receives during a chest X-ray were incorrect: the amount is 0.1 millisievert, not 0.1 microsievert. We also incorrectly state that a "six-hour transatlantic flight adds 0.5 and a whole-body CT scan 12 microsieverts": that should be millisieverts. In addition we wrongly spelled Masayoshi Son as "Sun" and incorrectly referred to the "Nagasaki Atomic Bomb Disease Hospital" when it is the (Japan red Cross) Atomic Bomb Hospital. Finally in a sentence comparing the distribution of caesium and strontium radioisotopes we wrongly suggested that strontium is heavier than caesium. However the atomic weight of strontium is 87.62 and that of caesium 132.9.