The story of Zatoichi follows the blind masseur (a guy who wonders around selling massages) known as Ichi with a habit for gambling and a dark secret; he is really the famous sword master Zatoichi; renowned for his lightning fast draw and his ability to defeat overwhelming numbers singlehandedly.
One of the most interesting things about Zatoichi is that it is not one film, nor even a trilogy; but a film series original released between 1962 and 1989, but with 3 or 4 remakes being made in recent years. Although the stories in each film is different, they all follow Ichi on his journeys as he helps the weak and oppressed, fights of dangerous sword masters and other thugs, and generally hacks up the bad guys. However each film still has a number of conventions that have become part of the Zatoichi franchise; Ichi will always go to a gambling joint and use his skilled hearing to get a lot of money, in each film there will be another skilled samurai or swordsman who is after Zatoichi for the challenge (including Toshiro Mifune, reprising his role as the Yojimbo in one of the better films of the series), and there will always be a villain or yakuza boss who has to be 'cut down a peg' (pardon the pun). In this respect, one could argue that there isn't much point in making a series because the films get repetitive.
THAT IS WRONG, stop thinking that this instant. The biggest impact of the Zatoichi films, apart from watching samurai sword fighting, is that each film is unique. In each film Ichi is on a different quest or mission and the story is original and separate to the others. The only trouble is that now a days you have to go to conventions to find copies of the films, or else spend hours trolling through the web. But do not give up on the idea of Zatoichi; even if you only find the modern remakes, it is well worth a couple of hours to watch sword slinging, life building stories that can easily be heralded as greatness.
