Naho Tsuchiya’s parents won’t be there to wish her luck when she starts high school next week. She and her little brother are now orphans, left to fend for themselves by Japan’s tsunami.

“There were four of us in the family. My mother, father, little brother and me,” she said.

“On the day of the tsunami Takashi was at the school with me, so he was safe. My parents took shelter in the sports hall. But that was washed away.”

Naho, 15, and Takashi, 13, are just two of an unknown number of children orphaned by the huge waves that crushed towns along Japan’s northeast coast on March 11. Hundreds, perhaps thousands of others lost one parent.

Naho knows for sure that her parents are gone.

“We found out about mum on the 12th and dad on the 14th,” she said.

With their house smashed to kindling and their possessions scattered around what was once the small city of Rikuzentakata, their dog Chakko is all that links the two children to life before the tsunami.

But Rikuzentakata’s tsunami defences were overwhelmed by the size and ferocity of the wave, which left around 2,300 people – 10 per cent of the town’s population – dead or missing.

After the tsunami, Naho and Takahashi spent a cold, frightened night on the floor of their school along with hundreds of others evacuated from their homes.

It was there that the young girl’s dance teacher spotted them and took them to her home, which sits on higher ground.

“I used to teach their father dancing as well, so I have known them since they were little,” said Shimizu Kiwako. “When I saw them at the school I thought it was awful, so I brought them here.”

The 74-year-old says she will take care of the children as long as necessary.

“It’s very sad for them and I worry about them,” she said. “They’re staying here so I try to look after them. I make them eat. But they are good children and they are trying to be cheerful.

Rikuzentakata city mayor Futoshi Toba said his staff were working hard to try to identify and cater for children whose parents were killed.

“We know more than 50 children have lost one or other of their parents,” he said.

“As far as we know at the moment, three or four children lost both of their parents.”

The government admits it does not know how many children were orphaned around the country.

The Welfare Ministry said it was establishing a working group to try to find out the scale of the task, Kyodo News reported. The wiping out of infrastructure and local government was complicating the task, he said, adding that the ministry was hoping to mobilise 400 experts to find nursing homes or foster parents for tsunami orphans.

For Naho, March should have been an exciting month.

She finished junior high school and was looking forward to the graduation ceremony that would mark her passage into the more grown up world of high school.

She says she is excited by the prospect of life at a larger school, but admits to being a little nervous and knows her future now rests on the kindness of relatives and neighbours. “The people around here have really helped me,” she said. “They are very kind.”

She talks vaguely of going to university, but speaks also of wanting to remain in Rikuzentakata when and if it is rebuilt.

Asked what she thinks will happen in the future, she pauses for a long time, before saying quietly: “I just want to do my best.”