(from ebookjapan):

Musashi (Takezo) was born in Miyamoto Village, Sangan County, Mimasaka Province (Okayama Prefecture), and spent his days being bullied by his stepmother. Taking advantage of his strength, he was a nuisance in the village, committing all kinds of violent acts.

One day, he is captured and punished by the monk Sozen of a nearby temple. Musashi was told by the monk that his strength was the strength of a monster, not a human being, and set off on a journey in search of what true strength was.

Shotaro Ishinomori vividly depicts the tumultuous life of Miyamoto Musashi!