Itō Ittōsai (伊東一刀斎, Itō Ittōsai?), 1560 - 1653?) was a famous yet mysterious Japanese swordsman rumored to have never lost a battle.[citation needed] He is attributed as the founder of the Ittō-ryū (lit. "one sword" or "one stroke") school of sword fighting.
Originally named Itō Yagorō, he at the age of fourteen found himself in a little seaside village called Izu. Legend tells that he floated across the Sagami Bay on a piece of driftwood from ōshima Island, part of the Izu Islands. The trust of the local villagers was earned when Yagorō chased away a group of bandits that went around raiding and pillaging. Desiring to be a great swordsman, the villagers paid for Yagorō's travels in seeking out a master. On his journey, Yagorō reached Tsurugaoka Hachiman-gū in Kamakura where he paid homage to the gods and practiced his swordsmanship. One particular day, an unknown assailant tried to attack Yagorō but he somehow unconsciously and without thinking drew his sword and cut him down in one swift stroke. Not understanding this technique, Yagorō would later describe it as "Musōken" (無想剣) a fundamental aspect of his swordsmanship's philosophy. Musōken is either an offensive or defensive posture that is delivered spontaneously and without thinking, fully anticipating an opponent's movement; a type of extra-sensory perception similar to mushin.
In another predicament, Ittōsai developed "Hosshato" when engaging multiple enemies in his bedroom. He would later change his name to "Itō Ittōsai Kagehisa." It is said Ittōsai's style evolved from the Chūjō-ryū style of his master, Kanemaki Jisai. Among the many pupils that Ittōsai trained, one such was his successor, Ono Tadaaki, who would go on to serve Tokugawa. The Itō-ryū style is grounded for some in Zen influence due to Ono Tadaaki's contact with the famed Buddhist priest, Takuan Sōhō. This is a reasonable assumption since later Itō-ryū swordsmen advocated directness and simplicity in their technique of the "one stroke."
Itō Ittōsai appears in the Japanese manga series Vagabond, as a former student of Kanemaki Jisai who broke off (from Jisai's [i]Chujō[/i]-ryu) and appears at various times throughout the 'Kojirō Arc' of Vagabond. Upon his return he subverts Jisai's upbringing of Kojiro by secretly bringing Kojirō to an encounter with other swordsmen, including Yoshioka Denshichirō and Ueda Ryōhei; eventually Jisai relented and allowed Ittōsai to assume the role of guiding Sasaki Kojirō's development as a master swordsman. In terms of his personality, Ittosai seems to possess some means of bloodlust, as he consistently encourages Kojirō to unleash his killer potential as a swordsman even in situations that are conditionally avoidable. Along the way he allowed Musō Gonnosuke Katsuyoshi to join them got them both into fighting in the aftermath of the Battle of Sekigahara (as well as their first-ever encounter with a young Shinmen Takezo), but he then 'abandoned' Kojirō to force the younger swordsman to survive on his own and neither Ittōsai nor Gonnosuke have been seen since.
Itō Ittōsai appears in the PlayStation 3 game Ryu ga Gotoku Kenzan!. At first he is known as simply Itoh, a local geisha house yojimbo, then after a duel with Miyamoto Musashi he reveals his true identity. In this game he is modelled after Susumu Terajima who also does his voice cast.