Possible Clues:

• Assassin hiding in town in Japan
• Nunchaku wielder in a martial arts film, maybe
• 14th-century Japanese warrior hired for espionage and assassinations
• 'Assassin in Japan' covers it
• Simone grapples with Jack, a martial art expert
• Far Eastern assassin
• Stealthy Japanese assassin
• Covert operator in unit measuring energy aboard old Spanish ship
• Stealthy spy or assassin in feudal Japan
• Stealthy killer