It's fiction. Kensuke's Kingdom takes you into a fictional world crafted by the author's creativity. There's no real-life basis for the story or its elements.
Indeed, 'Kensuke's Kingdom' is based on a real story. The author uses his personal experiences to create a vivid and believable world. He might have met someone like Kensuke in his travels, or perhaps experienced the feeling of being in a strange and unknown place himself. This real - life basis helps the readers to connect with the story on a deeper level, as they can imagine that such things could really occur.