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.

Zatoichi's Pilgrimage:
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.

From: Easy Going Scans

Ichi is a lone goze (blind woman singer) who has become separated from her traveling entertainment troupe. Wondering how she will find her place in life, she carries only a shamisen (a traditional Japanese stringed instrument) and a walking stick with a hidden blade inside. When necessary, she uses her exceptional sword skills to fight off yakuza and other villains.