was a Japanese swordsman who may have lived during the Azuchi–Momoyama and early Edo periods and is known primarily for the story of his battle with Miyamoto Musashi in 1612, where Sasaki was killed. Although suffering from defeat as well as death at the hands of Musashi, he is a revered and respected warrior in Japanese history and culture. Later Miyamoto proclaimed that Sasaki Kojirō was the strongest opponent he faced in his life.
History
Sasaki Kojirō went by the fighting name of , which was also the name of the kenjutsu school he had founded. It is said that Sasaki studied the Chūjō-ryu of sword fighting from either Kanemaki Jisai or Toda Seigen. Toda Seigen was a master of the kodachi. If Sasaki had indeed learned Chūjō-ryu from Seigen, he would have been his master's sparring partner. Due to his master's use of the kodachi, Sasaki used a nodachi, or a long katana, against him, therefore eventually excelling in its use. It was after defeating his master's younger brother that he left and founded the Ganryū. The first reliable account of his life states that in 1610, because of the fame of his school and his many successful duels, including once in the late 1500s when he fended off three opponents with a tessen, Sasaki was honored by Lord Hosokawa Tadaoki as the chief weapons master of the Hosokawa fief in the north of Kyūshū. Sasaki later became skilled in wielding a nodachi, and used one he called monohoshizao ("The Laundry-Drying Pole") as his strongest main weapon.
Duel with Miyamoto Musashi
Sasaki was a long-time rival of Miyamoto Musashi, and is considered (by Musashi himself) the most challenging opponent Musashi ever faced. There are a number of accounts of the duel, varying in most details except the essentials, such as Kojirō's defeat. The age of Kojirō is especially uncertain – the Nitenki says that during his childhood, he
The Nitenkis account initially seems trustworthy, until it goes on to give the age of Sasaki at the time of the duel as 18 years old; it is known that two years earlier he had been a head weapons master for a fief – but then that would imply he had reached such a position at the age of 16, which is extremely improbable. A further complication is that Toda Seigen died in the 1590s. This unreliability of the sources means Sasaki's age could have varied anywhere from his 20s to as late as his 50s. Even worse, a number of scholars contend that identifying Seigen as Kojirō's teacher is a mistake and that he was actually trained by a student of Seigen's, Kanemaki Jisai. The reason for this was that the person interviewed for the Nitenki (the last known witness to the duel) said Kojirō's age but the author missed the first part, and only got the last part which was 18 (十八), pronounced as "juu hachi" - however, numbers in Japanese are spoken as tens and ones, such as 48 (四十八) "yonjuuhachi". The reason his last name is Sasaki can be because of two reasons: His mother was a member of the Sasaki clan and had him out of wedlock. Since they were not married, he took on his mother's last name. She later married a distant cousin who also shared the same last name, and raised him as his own son. His mother was unaware she was pregnant with him when she married into the Sasaki clan. Thus, her husband, although suspecting the child wasn't his, raised him as his own son. Like his adversary Musashi, he was also very tall (about 5 ft. 10 in. or 1.78 m), a giant compared to the average Japanese at that time.
Apparently, the young Musashi, at the time, around 29 years old, heard of Sasaki's fame and asked Lord Hosokawa Tadaoki, through an intermediary, Nagaoka Sado Okinaga, a principal vassal of Tadaoki, to arrange a duel. Tadaoki assented and set the time and place as 13 April 1612 on the comparatively remote island of Ganryujima of Funashima, the strait between Honshū and Kyūshū. The match was probably set in such a remote place because by this time Sasaki had acquired many students and disciples, and were Sasaki to lose, they would probably have attempted to kill Musashi.