Chris Bradford 

Young Samurai: The Ring of Water is the fifth book in this blockbuster series by Chris Bradford. Jack Fletcher has been left for dead. Bruised and battered, Jack wakes up in a roadside inn wrapped only in a dirty kimono. He has lost everything, including his memory of what happened. Determined to discover the truth, Jack goes on a quest to retrieve his belongings—his precious swords, his friend Akiko's black pearl, and, most important of all, his father's prize possession. Relying on his samurai and ninja training, Jack realizes The Ring of Water is the key to his survival. But with only a washed up Ronin—a masterless samurai—for help, what will Jack manage to find? What will he lose? And what will he have to sacrifice?