Still remote, despite modernising moves, and with little real power, Japan's monarch none the less holds a unique place in the hearts of his people

When the emperor of Japan addresses his nation, you know there is a crisis. On 15 August 1945, a week after atomic bombs were dropped on Hiroshima and Nagasaki, Hirohito's radio address announcing the surrender of Japan was broadcast across the country. Until last week, however, no event in the country's history was considered traumatic enough for his son, Akihito, to perform a similar task.

All that changed last Wednesday when the consequences of Japan's biggest-ever recorded earthquake spurred the 77-year-old emperor into action with a televised call for concerted national action. For those old enough to remember Hirohito's Gyokuon-hoso ("Jewel Voice Broadcast"), it was a stark reminder of the gravity of Japan's situation. And in contrast to Hirohito's address, which had been couched in language familiar only to the well-educated and notable for a confusing lack of detail about the surrender itself, Akihito was clear in his message of hope.

Usually, the only chance to hear the emperor speak is during his New Year's speech or birthday address on 23 December, the only two days of the year when the public is permitted to enter the imperial palace. He appears on its balcony with members of his family in front of a jubilant crowd and gives what is typically a short speech, greeting and thanking the visitors and wishing them good health and blessings.

But last week's appearance was the first televised address to the nation by a man who, unlike his father, has deliberately sought to be an "ordinary" emperor. He is, after all, the first not to be considered an arahitogami, or incarnate divinity, a status his father was forced to reject by the US in 1945.

After Hirohito's death in 1989, Akihito ascended the Chrysanthemum Throne to become Japan's 125th emperor. In a period stretching back to the 7th century BC, the Imperial House of Japan is the oldest continuing hereditary monarchy in the world.

Unlike the British monarchy, the emperor is severely restricted by his constitutional position, with one article stating he can perform only "acts in matters of state as are provided for in the constitution and he shall not have powers related to government".

Despite those constraints, the desire to connect with his people has been a theme throughout Akihito's life. Taught English and western culture by an American tutor, Elizabeth Gray Vining, he later studied political science at Gakushuin University in Tokyo, but never received a degree.

His ultimate modernising move came in 1959, when the then 25-year-old Akihito broke with a 1,000-year tradition and married a commoner, Michiko Shoda, thanks to the overturn of the Meiji-era imperial household laws at the end of the Second World War. The couple went on to have two sons, Naruhito and Akishino, and a daughter, Sayako.

But where some traditions were broken, others remain steadfastly in place. No emperor is ever referred to by name; instead, Japanese people call the emperor "Tenno", literally, "heavenly sovereign", during his reign. After the emperor's death, they are named after an era chosen for them; thus Hirohito is known exclusively in Japan as Showa Emperor. By custom, Akihito will be known as Heisei Emperor by order of the cabinet after his death.

His reign provides continuity where successive governments offer instability. Since the Meiji Restoration of 1868, there have been 61 prime ministers of Japan, with 15 alone since Akihito became emperor in 1989.

I lived in Japan for some years and heard a scepticism among people towards politicians that simply does not exist for the most part towards the imperial family. In recent days, the government and Tokyo Electric Power Company (Tepco) have come under fierce criticism over the issue of whether they are providing people with enough information about events in Fukushima. But Akihito injected calm where there had been fear.

"The number of people killed is increasing day by day and we do not know how many people have fallen victim," Akihito said, adding that he was praying for his people and his country.

In the aftermath of his national address, the Japanese response on the internet was full of praise. "The royal family preserves a way of life that no other political or other public figure can," said one. "They speak polite and beautiful Japanese. The emperor is not seen as a deity any more, but as a symbol all Japanese can respect. The reaction to his TV speech was overwhelmingly positive. People thought he chose very thoughtful words – it made people emotional and people were encouraged to hear what he had to say."

Many in the west had quite possibly almost forgotten the Japanese imperial family existed, so relatively low has their international profile been in recent years. The one story most non-Japanese people associate with it is the health problems of Crown Princess Masako and the pressure on her to produce a male heir. In his birthday address of 2004, Akihito seemed to suggest he was fed up with Crown Prince Naruhito and his wife criticising his eldest son for speaking in public earlier that year of the "suffocating atmosphere" in the royal household which he claimed had contributed to his wife's clinical depression.

Masako, a promising diplomat until her marriage, has rarely been seen in public during the last decade, since her only child, Princess Toshi, was born in 2001. A male heir finally arrived in 2006 when Hisahito was born to Prince and Princess Akishino, an event hailed by royalists as forestalling the imperial succession crisis.

But despite successful efforts to modernise the imperial family, many Japanese people still view their royal family with detachment. One friend from Japan, Hiroko Fukamachi-Self, told me she thought they lived in a different world.

"When I was at elementary school, I liked to watch the TV programme about the royal family every Saturday morning," she said. "I couldn't see any emotion from their face. They wore their smiles like a mask. It never changed."

For the 1.5 million Okinawans in the southern tropical islands of Japan, the imperial family is viewed with suspicion because of the islanders' horrific treatment at the hands of the imperial army, of which the emperor was nominally in charge, during the Second World War. Hirohito never visited Okinawa, where troops exposed civilians to a war in which a third of the population died. It was the only prefecture in Japan in which he never set foot, although plans were being made for him to do so shortly before his death. In 1993, Akihito became the first emperor to go to Okinawa. He had paid several visits as crown prince, surviving an assassination attempt in 1975, when he and Michiko narrowly escaped a petrol bomb thrown at them by an extremist.

For those who never got the chance to see Hirohito, it was an opportunity to vent anger built up over 30 years. But seeing Akihito's reaction to the attack changed many people's opinion of the royal household. The mask slipped and the human emotion poured out. "I remember seeing the emperor crying in Okinawa," said Hiroko. "There are a lot of people who still hate Akihito's father in Okinawa because of the war. Akihito and Michiko came back to the cenotaph a few hours after the attack and showed their tears. It was the first time that I saw any emotion from them and I felt they are human, like us.

"I felt they are close to us. Their world is so shuttered from ours. I feel sorry for them sometimes. They can't go out shopping, go on a date, go out to drink or do normal stuff. The emperor is not a doctor but he has some special power to heal our wounded mind. He is our moral support."

Following the Kobe earthquake in 1995, which killed 6,400 people, Akihito visited survivors living in an emergency shelter in a school gym. Dressed casually in a sweater and light jacket, he knelt to comfort the victims and held their hands, telling them: "Don't give up hope."

In recent years, several people have posted questions on Japanese website forums asking whether the country still needs an emperor. The responses have always been emphatic – the emperor is an integral part of the nation's life. Last Wednesday, Akihito reappeared with the same message he gave to those victims of the Kobe disaster, but this time to the whole country: Japan – do not lose hope.