Who was Zatoichi??

Shintaro Katsu in Zatoichi Challenged (1967)

Zatoichi (Zatōichi) is a fictional character featured in one of Japan's longest running series of films and a television series set in the Edo period. The enduring popularity of the character has been likened to that of James Bond in Western countries. Unlike Bond, however, whose character has been portrayed by a long list of actors, Zatoichi has become almost synonymous with only one actor: Shintaro Katsu.

Zatoichi seems to be only a harmless blind anma (masseur) who wanders around the country making his living by gambling; however, he is also highly-skilled in swordsmanship, specifically iaijutsu. he does not carry a traditional katana, instead using a well-made shikomizue (cane sword). Shikomizue were generally straight lower-quality blades which could not compare with regular katanas, but as revealed in Zatoichi's Cane Sword, his weapon is nearly superiour to one as it was forged by a master bladesmith just before his prime.
A recurring theme of both the films and television series is Zatoichi protecting the innocent from oppressive warring yakuza gangs, and general injustice. His fighting skill is incredible, even more so considering he grips the sword in an inverse manner; this combined with his sometimes inexplicably keen ear, nose and propioception renders him a capable surprise attacker.

The character's name is actually Ichi. Zatō is a title, the lowest of the four official ranks within the Todoza, the historical guild for blind men. Ichi is therefore properly called Zatō-no-Ichi ("Low-Ranking Blind Person Ichi", approximately), or Zatōichi for short. It is also a play on words: 'Sa' or 'za' is a combinative word for master; 'to' is likewise for sword; therefore, an alternate translation might read 'First Sword Master'. Giving massages was a traditional occupation for the blind, since blind persons and masseurs were on the lowest societal level, equal to or slightly above beggars.