The Ring of Water is the fifth book in the Young Samurai Series.
It was released in March 2011.
Bruised and battered, Jack Fletcher 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 realises 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?
- Ronin - Seemingly just another masterless samurai. However, his past was tragic. A spy disguised as a monk killed his father, Obata Torayasu, and Ronin failed to protect him. Hence he took to drinking sake to forget his guilt at being helpless. This incident also caused him to foster a hatred for monks, which drove him to join Botan's gang upon hearing of a monk (Jack) dressed as a spy in the vicinity after he desperately needed work. What he didn't expect was that Botan would backstab him by drugging his sake and wiping his memory of their trap laid upon Jack for the most part of the book. Eventually becomes Jack's firm friend.
- Hana - A highly skilled thief and also a hinin (outcast) that Ronin and Jack meet on their journey. At first she was an unwilling captive of the two, but quickly proved her worth with her quick wits, especially when Daimyo Sanada tried to take their lives. Jack would eventually entrust her with his inro to warn Akiko that Kazuki was targeting her to kill as well. She was last seen departing for Toba, where Akiko and family reside in. In the Ring of Fire, it was revealed that she got lost in the Iga mountains and chanced upon Shonin's ninja clan. After some explanation as to how she knew Jack, Hanzo was tasked to guide her to Toba.
- Riddling Monk - A devious looking character who was in possession of Jack's rutter . Has a huge following of disciples. He did encounter a drunk Ronin at some point, and took the rutter away from him. Ronin failed to get back the book since he answered the Monk's riddle incorrectly. Jack and Hana would get the rutter back by answering his 3 riddles late in the book. Resides in a ruined temple on a stormy mountaintop.
- Matagoro Araki - Samurai at the Yagyu Ryu who is in possession of Jack's daisho, and challenged him to a duel which Jack won.
- Botan - Skilled and ruthless samurai , leader of the group that assaulted Jack and robbed him of his possessions. He hired Ronin as part of his plan, but drugged his sake as well as cover.
- Sanada - Daimyo of Nara Province. Challenged Jack to a game of go, or Japanese Chess. His flag is black and white checks, as is the rest of his palace and his clothes.