The Ring of Fire (Young Samurai #6) by Chris Bradford
Jack Fletcher faces his toughest challenge yet. After a snowstorm forces him to take shelter, Jack comes across a village in need of protection from raiding mountain bandits. Torn between moving on or helping, Jack is persuaded to stay and fight the villagers' cause. But Jack is the first and only samurai to do so. Now he must enlist other warriors to the villagers' aid before the bandits return to steal their harvest. No easy task when the reward is so little and he is a foreigner. If only he had his friends to call on. . . Using the Ring of Fire, can Jack overpower the bandits and win?