On the penultimate day of his Japan trip, the pontiff heard the stories of those who survived the so-called "triple disaster" -- a 9.1-magnitude earthquake that triggered a devastating tsunami and sent a nuclear plant into meltdown.

In an emotional meeting, he embraced 17-year-old Matsuki Kamoshita, who spoke powerfully of his experience as an evacuee, saying he was so badly bullied he "wanted to die."

The 82-year-old Argentine paid tribute to those who rushed to help following the disaster, but warned that more was needed.

"No one 'rebuilds' by himself or herself; nobody can start over alone. We have to find a friendly and fraternal hand, capable of helping to raise not just a city, but also our horizon and our hope."

Some 18,500 were killed or are missing after the disaster. The waves swept away homes and farms, and engulfed the cooling systems at the Fukushima Daiichi power plant, triggering the worst nuclear disaster since Chernobyl.

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.

Survivors shared painful memories of the disaster, with Toshiko Kato recalling finding her home had been swept away by the waves.

"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," she told the pope.

- 'Concern' on nuclear power -

The head of the world's 1.3 billion Catholics stopped short of intervening in the debate over nuclear power in Japan, but said there were "important decisions" to be made about future energy sources.

"In turn, this involves, as my brother bishops in Japan have emphasised, concern about the continuing use of nuclear power; for this reason, they have called for the abolition of nuclear power plants," he said.

After the meeting, Kamoshita told reporters he had been "deeply touched" to discover the pope remembered meeting him at the Vatican earlier this year.

Francis later met with youth at a Tokyo cathedral, where he repeated a warning he sounded on the first leg of his Asia tour in Thailand on the pitfalls of technology.

He called on young people to reach out to others and not isolate themselves.

"We have invented all sorts of gadgets but we still can't take selfies of the soul," he said, during a relaxed visit that saw him don a colourful traditional Japanese shirt over his white papal robes and give a thumbs-up.

In the afternoon, tens of thousands of the faithful and the curious flocked to a mass at the Tokyo Dome, waving Japanese and Vatican flags as the pope entered in an open-top vehicle.

He waved to the diverse crowd of Japanese and foreign attendees, smiling broadly and kissing the heads of children held up to him as he passed.

- A call to connect -

In his address, Francis drove home his call for people to connect with one another, highlighting the plight of the "many people who are socially isolated" in Japan.

"They remain on the margins, unable to grasp the meaning of life and their own existence," he said.

"The home, school and community, which are meant to be places where we support and help one another, are being eroded by excessive competition in the pursuit of profit and efficiency."

The message may be particularly pertinent in Japan, notorious for its long working hours. The government is already encouraging employers to give workers more freedom to pursue family lives, hoping to boost the country's dwindling birth rate.

The pope began his trip in Nagasaki and Hiroshima, where he called the use of nuclear weapons a "crime," against the backdrop of two cities synonymous with the atomic bomb's destruction.

The final day of his visit on Tuesday includes meetings with young students at Sophia University, before he concludes his Asian tour.

bur-sah/ric/aph

TOKYO DOME