(CNN)--Kenichi Kurosawa clung precariously to a tree as the water rose around him, entirely flooding the roads below.

For almost six minutes on March 11, 2011, a 9.1 magnitude earthquake -- the worst to ever hit Japan -- struck 370 kilometers (230 miles) northeast of Tokyo, triggering a huge tsunami that crashed into Ishinomaki, the coastal city Kurosawa had lived in his whole life.

Minutes before waves up to 10 meters (nearly 30 feet) high swept in, Kurosawa, then aged 40, had scrambled 3 meters (10 feet) up a pine tree, wrapped his legs around a branch and hung on for his life.

"I felt like the ocean was all around me. The water was so cold it chilled me to the bone," he recalls.

As the water came up to his knees, Kurosawa saw people in cars gripping their steering wheels as their vehicles were washed down the road. Others who had been hanging on to trees felled by the waves were swept away. For hours, Kurosawa endured sub-zero temperatures. He thought of his wife -- he'd reached her on her cellphone for 15 seconds while in the tree, before the line went dead.