Clinton and the Kappa

In this book, a boy from Florida is visiting with relatives in Japan. He has a cousin (i think) who is about the same age. The two are at the beach one day, when a kappa steals their beach ball. When Clinton is looking for the beach ball, he is almost dragged into the water by the Kappa. Then, Clinton's cousin defeats the kappa, but they realize they need to help the defeated Kappa. Then, they all are friends. The End. I personally think it is a little morbid at some parts, but the rest s a cute little children's story.