Norio Kimura, 50, who lost his father, wife and daughter in the March 11, 2011 tsunami, looks at his family's personal belongings at a temple near his home inside the exclusion zone in Okuma, near Tokyo Electric Power Co's (TEPCO) tsunami-crippled Fukushima Daiichi nuclear power plant, Fukushima Prefecture, Japan, Feb 14, 2016. [Photo/Agencies]

On a recent weekend, Kimura and a dozen volunteers led by Ueno, combed through piles of debris on a windswept Okuma beach for any signs of Yuna. They are allowed to enter the area up to 30 times a year and stay for up to five hours per visit.

As they dug through heaps of dirt mixed with driftwood, blocks of concrete, utility poles, crooked iron pipes and clothes of all sizes and colours, a dosimetre emitted high-pitched beeps. At one point, it showed six microsieverts per hour, 100 times as high as radiation levels in downtown Tokyo.

That does not shake Kimura's resolve.