The series stars a teenage martial artist named Sanshiro, trained in the Kurenai School of Jiujitsu and centers around his search for his father's killer. Accompanying Sanshiro is an orphaned boy named Kenbo and his pet dog Boke. Sanshiro's only clue to his father's murderer is a glass eye left on the scene of the crime, suggesting that his father's murderer was one-eyed. Thus many of the villains Sanshiro fought during the course of the series were one-eyed or had one eye concealed with an eye-patch.