Zen: He finds Logan in jail in Canada and makes him an offer he can't refuse - to come to Japan and learn about his origin.
Shingen: His late father was the Master of the Hand, but rather than allow Shingen to take on the role, he killed himself and left the Hand master-less, hoping that they would choose Logan as their new Master.
Kenuichio/Samurai: He's the illegitimate son of Shingen, but Shingen refuses to acknowledge him as an heir. He's also an expert Samurai, and he attacks Logan several times as a "Silver Samurai" with electrified armor.
Mariko: Shingen's daughter. Shingen has arranged her marriage to the corrupt Noburo, but when Logan saves her life, they fall for one another.
Noburo Moro: Minister of Justice. He's corrupt - in the back pocket of the Yakuza - and Shingen's arranged for him to marry Mariko.
Viper: Noburo's secretary. She's in league with both Shingen and Kenuichio, her lover, but she's ultimately more loyal to Shingen.
Yukio: Logan's bodyguard. They have an immediate physical attraction. She's also still partially loyal to Shingen and reports back to him, but she's more loyal to Logan, who she considers her master.
Frank Sinatra: A Yakuza higher-up who provides Logan with information.