This manga is the adaptation of two movies: Zatoichi's Vengeance (Tokuzo Tanaka) and Zatoichi's Pilgrimage (Kazuo Ikehiro).
The Ballad of Zatoichi
Zatoichi comes upon a dying man who asks him to give a bag of money to "Taichi." Zatoichi has no idea who this is but when he comes upon a small town harassed by gangsters, he finds that "Taichi" was the man's young son. Along his travels, he also met a blind monk who makes Zatoichi question his murderous lifestyle. In trying to help the town, Zatoichi kills some gangsters and becomes a hero to the boy. He must make a choice of whether to stay and defend the town or to leave and be on his way.
After he's ambushed in a small village terrorized by a gang of thieves, the legendary blind swordsman Zatoichi is forced to kill a young man in self-defense. As fate would have it, his travels soon lead him to Okichi, a woman whom Zatoichi discovers is the sister of the young man whose life he stole. In anger, Okichi attacks the blind swordsman, but her conscience gets the better of her, and as she tends his wounds, the two fall in love.