Toshiko Kato was at her job as head of a Catholic kindergarten in Iwate region when the quake and tsunami hit on March 11, 2011. The massive waves that killed nearly 16,000 people caused enormous destruction, including sweeping away her home.

"That morning, I could not have known that the daily life I had known before I left the house would end, that in an instant many people would die," she told Francis.

"I remember that when I stood in the rubble where my home had been, I was thankful for being given life, for being alive, and for just being able to appreciate it."

And Kato said she felt she had "received much more than I lost."

"Many people from all over the world opened their hearts and I was able to find hope from seeing people come together to help one another," she said.

"Life is the most important thing, and no good life is lost."

The human cost of the quake and tsunami was enormous -- with 18,500 dead or missing. The meltdown itself killed no one, but more than 3,700 people who survived the triple disaster later died as a result of complications related to evacuations.

Nearly half a million people fled their homes in the first days after the quake and even today, roughly 50,000 remain in temporary housing.

- 'I wanted to die' -

Among those forced to evacuate was Matsuki Kamoshita, who was eight when the nuclear meltdown happened.

His father, a teacher, remained in Fukushima region to help his students, while Kamoshita and his three-year-old brother moved from place to place with their mother.

"My brother would burrow into his futon and cry. I was bullied... and every day was so painful I wanted to die," he told Francis, speaking steadily before the crowd.

"Eventually, my father got mentally and physically ill and stopped working. Even so, I still think we are fortunate because we were able to evacuate."

Japan's government has been encouraging people who evacuated to return to areas that have now been declared safe after extensive decontamination.

But many fear their former homes are not really safe, and others are reluctant to return to what have in some cases become ghost towns, with few services, particularly for young families.

In his address to survivors, Francis called for renewed efforts to support the victims of the disaster.

"In this way, those who are suffering will be supported and know that they have not been forgotten," he said.

"We cannot fully convey our suffering," Kamoshita told Francis, who he hugged after delivering his remarks.

"Pray with us, Holy Father, that we can appreciate each other's pain and love our neighbours. Pray that even in this cruel reality, we will be given the courage not to turn our eyes away."