Known as the "Hundred Man Killer", Manji was a renowned swordsman in feudal Japan who took countless innocent lives. What was even more remarkable, however, was his ability to withstand any injury. This was thanks to the bloodworms that had been surgically implanted in his body by an ancient nun named Yaobikuni who was over eight hundred years old. In an effort to atone for his past misdeeds, Manji made a vow to rid the world of one thousand evil men. Yaobikuni promised to lift the curse of his immortality if he succeeded in his task. One day, Rin Asano, a sixteen-year-old girl, begged him to help her avenge her parents' brutal murder. At first, Manji refused her plea, but when he realized how vulnerable she was, he had a change of heart. He promised to protect her for the next four years as they embarked on a dangerous journey to seek redemption, exact revenge on their foes and accomplish their life's purpose.