Is kensuke a real man (book by micheal morphugo)

The author answered this question here: https://www.mumsnet.com/qanda/michael-morpurgo
"What is true is that there was a Japanese soldier who stayed behind on an island in the Pacific after WW2. He was there for 40 years! All on his own! Yes, people fall off boats, yes orangutans are hunted for their babies, yes little turtles have to make a run for the sea when they hatch out. But the rest I made up."